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# -*- coding: utf-8 -*- r""" Heegner points on elliptic curves over the rational numbers
AUTHORS:
- William Stein (August 2009)-- most of the initial version
- Robert Bradshaw (July 2009) -- an early version of some specific code
EXAMPLES::
sage: E = EllipticCurve('433a') sage: P = E.heegner_point(-8,3) sage: z = P.point_exact(201); z (-4/3 : 1/27*a - 4/27 : 1) sage: parent(z) Abelian group of points on Elliptic Curve defined by y^2 + x*y = x^3 + 1 over Number Field in a with defining polynomial x^2 - 44*x + 1159 sage: parent(z[0]).discriminant() -3 sage: E.quadratic_twist(-3).rank() 1 sage: K.<a> = QuadraticField(-8) sage: K.factor(3) (Fractional ideal (1/2*a + 1)) * (Fractional ideal (-1/2*a + 1))
Next try an inert prime::
sage: K.factor(5) Fractional ideal (5) sage: P = E.heegner_point(-8,5) sage: z = P.point_exact(300) sage: z[0].charpoly().factor() (x^6 + x^5 - 1/4*x^4 + 19/10*x^3 + 31/20*x^2 - 7/10*x + 49/100)^2 sage: z[1].charpoly().factor() x^12 - x^11 + 6/5*x^10 - 33/40*x^9 - 89/320*x^8 + 3287/800*x^7 - 5273/1600*x^6 + 993/4000*x^5 + 823/320*x^4 - 2424/625*x^3 + 12059/12500*x^2 + 3329/25000*x + 123251/250000 sage: f = P.x_poly_exact(300); f x^6 + x^5 - 1/4*x^4 + 19/10*x^3 + 31/20*x^2 - 7/10*x + 49/100 sage: f.discriminant().factor() -1 * 2^-9 * 5^-9 * 7^2 * 281^2 * 1021^2
We find some Mordell-Weil generators in the rank 1 case using Heegner points::
sage: E = EllipticCurve('43a'); P = E.heegner_point(-7) sage: P.x_poly_exact() x sage: P.point_exact() (0 : 0 : 1)
sage: E = EllipticCurve('997a') sage: E.rank() 1 sage: E.heegner_discriminants_list(10) [-19, -23, -31, -35, -39, -40, -52, -55, -56, -59] sage: P = E.heegner_point(-19) sage: P.x_poly_exact() x - 141/49 sage: P.point_exact() (141/49 : -162/343 : 1)
Here we find that the Heegner point generates a subgroup of index 3::
sage: E = EllipticCurve('92b1') sage: E.heegner_discriminants_list(1) [-7] sage: P = E.heegner_point(-7); z = P.point_exact(); z (0 : 1 : 1) sage: E.regulator() 0.0498083972980648 sage: z.height() 0.448275575682583 sage: P = E(1,1); P # a generator (1 : 1 : 1) sage: -3*P (0 : 1 : 1) sage: E.tamagawa_product() 3
The above is consistent with the following analytic computation::
sage: E.heegner_index(-7) 3.0000? """
#***************************************************************************** # Copyright (C) 2005-2009 William Stein <wstein@gmail.com> # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 2 of the License, or # (at your option) any later version. # http://www.gnu.org/licenses/ #***************************************************************************** from __future__ import print_function, absolute_import from six.moves import range
from sage.misc.all import verbose, prod from sage.misc.cachefunc import cached_method
from sage.structure.sage_object import SageObject from sage.structure.richcmp import (richcmp_method, richcmp, richcmp_not_equal, rich_to_bool)
import sage.rings.number_field.number_field_element import sage.rings.number_field.number_field as number_field import sage.rings.all as rings from sage.rings.all import (ZZ, GF, QQ, CDF, Integers, RealField, ComplexField, QuadraticField, is_fundamental_discriminant) from sage.arith.all import (gcd, xgcd, lcm, prime_divisors, factorial, binomial) from sage.quadratic_forms.all import (BinaryQF, BinaryQF_reduced_representatives) from sage.matrix.all import MatrixSpace, matrix
from sage.modular.modsym.p1list import P1List
################################################################################## # # The exported functions, which are in most cases enough to get the # user going working with Heegner points: # # heegner_points -- all of them with given level, discriminant, conducto # heegner_point -- a specific one # ##################################################################################
def heegner_points(N, D=None, c=None): """ Return all Heegner points of given level `N`. Can also restrict to Heegner points with specified discriminant `D` and optionally conductor `c`.
INPUT:
- `N` -- level (positive integer)
- `D` -- discriminant (negative integer)
- `c` -- conductor (positive integer)
EXAMPLES::
sage: heegner_points(389,-7) Set of all Heegner points on X_0(389) associated to QQ[sqrt(-7)] sage: heegner_points(389,-7,1) All Heegner points of conductor 1 on X_0(389) associated to QQ[sqrt(-7)] sage: heegner_points(389,-7,5) All Heegner points of conductor 5 on X_0(389) associated to QQ[sqrt(-7)] """ raise TypeError
def heegner_point(N, D=None, c=1): """ Return a specific Heegner point of level `N` with given discriminant and conductor. If `D` is not specified, then the first valid Heegner discriminant is used. If `c` is not given, then `c=1` is used.
INPUT:
- `N` -- level (positive integer)
- `D` -- discriminant (optional: default first valid `D`)
- `c` -- conductor (positive integer, optional, default: 1)
EXAMPLES::
sage: heegner_point(389) Heegner point 1/778*sqrt(-7) - 185/778 of discriminant -7 on X_0(389) sage: heegner_point(389,-7) Heegner point 1/778*sqrt(-7) - 185/778 of discriminant -7 on X_0(389) sage: heegner_point(389,-7,5) Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) sage: heegner_point(389,-20) Heegner point 1/778*sqrt(-20) - 165/389 of discriminant -20 on X_0(389) """
################################################################################## # # Ring class fields, represented as abstract objects. These do not # derive from number fields, since we do not need to work with their # elements, and explicitly representing them as number fields would be # far too difficult. # ##################################################################################
class RingClassField(SageObject): """ A Ring class field of a quadratic imaginary field of given conductor.
.. NOTE::
This is a *ring* class field, not a ray class field. In general, the ring class field of given conductor is a subfield of the ray class field of the same conductor.
EXAMPLES::
sage: heegner_point(37,-7).ring_class_field() Hilbert class field of QQ[sqrt(-7)] sage: heegner_point(37,-7,5).ring_class_field() Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: heegner_point(37,-7,55).ring_class_field() Ring class field extension of QQ[sqrt(-7)] of conductor 55
TESTS::
sage: K_c = heegner_point(37,-7).ring_class_field() sage: type(K_c) <class 'sage.schemes.elliptic_curves.heegner.RingClassField'> sage: loads(dumps(K_c)) == K_c True """ def __init__(self, D, c, check=True): """ INPUT:
- `D` -- discriminant of quadratic imaginary field
- `c` -- conductor (positive integer coprime to `D`)
- ``check`` -- bool (default: ``True``); whether to check validity of input
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.RingClassField(-7,5, False) Ring class field extension of QQ[sqrt(-7)] of conductor 5
"""
def __eq__(self, other): """ Used for equality testing.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: K5 = E.heegner_point(-7,5).ring_class_field() sage: K11 = E.heegner_point(-7,11).ring_class_field() sage: K5 == K11 False sage: K5 == K5 True sage: K11 == 11 False """
def __ne__(self, other): """ Check whether ``self`` is not equal to ``other``.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: K5 = E.heegner_point(-7,5).ring_class_field() sage: K11 = E.heegner_point(-7,11).ring_class_field() sage: K5 != K11 True sage: K5 != K5 False sage: K11 != 11 True """
def __hash__(self): """ Used for computing hash of ``self``.
.. NOTE::
The hash is equal to the hash of the pair ``(discriminant, conductor)``.
EXAMPLES::
sage: E = EllipticCurve('389a'); K5 = E.heegner_point(-7,5).ring_class_field() sage: hash(K5) == hash((-7,5)) True """
def conductor(self): """ Return the conductor of this ring class field.
EXAMPLES::
sage: E = EllipticCurve('389a'); K5 = E.heegner_point(-7,5).ring_class_field() sage: K5.conductor() 5 """
def discriminant_of_K(self): """ Return the discriminant of the quadratic imaginary field `K` contained in ``self``.
EXAMPLES::
sage: E = EllipticCurve('389a'); K5 = E.heegner_point(-7,5).ring_class_field() sage: K5.discriminant_of_K() -7 """
@cached_method def ramified_primes(self): r""" Return the primes of `\ZZ` that ramify in this ring class field.
EXAMPLES::
sage: E = EllipticCurve('389a'); K55 = E.heegner_point(-7,55).ring_class_field() sage: K55.ramified_primes() [5, 7, 11] sage: E.heegner_point(-7).ring_class_field().ramified_primes() [7] """
def _repr_(self): """ EXAMPLES::
sage: heegner_point(37,-7,55).ring_class_field()._repr_() 'Ring class field extension of QQ[sqrt(-7)] of conductor 55' sage: heegner_point(37,-7).ring_class_field()._repr_() 'Hilbert class field of QQ[sqrt(-7)]' """ else:
@cached_method def degree_over_K(self): """ Return the relative degree of this ring class field over the quadratic imaginary field `K`.
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7,5) sage: K5 = P.ring_class_field(); K5 Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: K5.degree_over_K() 6 sage: type(K5.degree_over_K()) <... 'sage.rings.integer.Integer'>
sage: E = EllipticCurve('389a'); E.heegner_point(-20).ring_class_field().degree_over_K() 2 sage: E.heegner_point(-20,3).ring_class_field().degree_over_K() 4 sage: kronecker(-20,11) -1 sage: E.heegner_point(-20,11).ring_class_field().degree_over_K() 24 """
# Multiply class number by relative degree of the Hilbert class field H over K.
@cached_method def degree_over_H(self): """ Return the degree of this field over the Hilbert class field `H` of `K`.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: E.heegner_point(-59).ring_class_field().degree_over_H() 1 sage: E.heegner_point(-59).ring_class_field().degree_over_K() 3 sage: QuadraticField(-59,'a').class_number() 3
Some examples in which prime dividing c is inert::
sage: heegner_point(37,-7,3).ring_class_field().degree_over_H() 4 sage: heegner_point(37,-7,3^2).ring_class_field().degree_over_H() 12 sage: heegner_point(37,-7,3^3).ring_class_field().degree_over_H() 36
The prime dividing c is split. For example, in the first case `O_K/cO_K` is isomorphic to a direct sum of two copies of ``GF(2)``, so the units are trivial::
sage: heegner_point(37,-7,2).ring_class_field().degree_over_H() 1 sage: heegner_point(37,-7,4).ring_class_field().degree_over_H() 2 sage: heegner_point(37,-7,8).ring_class_field().degree_over_H() 4
Now c is ramified::
sage: heegner_point(37,-7,7).ring_class_field().degree_over_H() 7 sage: heegner_point(37,-7,7^2).ring_class_field().degree_over_H() 49
Check that :trac:`15218` is solved::
sage: E = EllipticCurve("19a"); sage: s = E.heegner_point(-3,2).ring_class_field().galois_group().complex_conjugation() sage: H = s.domain(); H.absolute_degree() 2 """
# Let K_c be the ring class field. We have by class field theory that # Gal(K_c / H) = (O_K / c O_K)^* / ((Z/cZ)^* M), # where M is the image of the roots of unity of K in (O_K / c O_K)^*. # # To compute the cardinality of the above Galois group, we # first reduce to the case that c = p^e is a prime power # (since the expression is multiplicative in c). # Of course, note also that #(Z/cZ)^* = phi(c) # # Case 1: p splits in O_K. Then # #(O_K/p^e*O_K)^* = (#(Z/p^eZ)^*)^2 = phi(p^e)^2, so # #(O_K/p^e*O_K)^*/(Z/p^eZ)^* = phi(p^e) = p^e - p^(e-1) # # Case 2: p is inert in O_K. Then # #(O_K/p^e O_K)^* = p^(2*e)-p^(2*(e-1)) # so #(O_K/p^e*O_K)^*/(Z/p^eZ)^* # = (p^(2*e)-p^(2*(e-1)))/(p^e-p^(e-1)) = p^e + p^(e-1). # # Case 3: p ramified in O_K. Then # #(O_K/p^e O_K)^* = p^(2*e) - p^(2*e-1), # so #(O_K/p^e O_K)^*/#(Z/p^eZ)^* = p^e. # # Section 4.2 of Cohen's "Advanced Computational Algebraic # Number Theory" GTM is also relevant, though Cohen is working # with *ray* class fields and here we want the cardinality # of the *ring* class field, which is a subfield.
# split case else: # ramified case else: # inert case
@cached_method def absolute_degree(self): r""" Return the absolute degree of this field over `\QQ`.
EXAMPLES::
sage: E = EllipticCurve('389a'); K = E.heegner_point(-7,5).ring_class_field() sage: K.absolute_degree() 12 sage: K.degree_over_K() 6 """
degree_over_Q = absolute_degree
@cached_method def quadratic_field(self): r""" Return the quadratic imaginary field `K = \QQ(\sqrt{D})`.
EXAMPLES::
sage: E = EllipticCurve('389a'); K = E.heegner_point(-7,5).ring_class_field() sage: K.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 """
@cached_method def galois_group(self, base=QQ): """ Return the Galois group of ``self`` over base.
INPUT:
- ``base`` -- (default: `\QQ`) a subfield of ``self`` or `\QQ`
EXAMPLES::
sage: E = EllipticCurve('389a') sage: A = E.heegner_point(-7,5).ring_class_field() sage: A.galois_group() Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: B = E.heegner_point(-7).ring_class_field() sage: C = E.heegner_point(-7,15).ring_class_field() sage: A.galois_group() Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: A.galois_group(B) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 over Hilbert class field of QQ[sqrt(-7)] sage: A.galois_group().cardinality() 12 sage: A.galois_group(B).cardinality() 6 sage: C.galois_group(A) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 15 over Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: C.galois_group(A).cardinality() 4
"""
def is_subfield(self, M): """ Return ``True`` if this ring class field is a subfield of the ring class field `M`. If `M` is not a ring class field, then a TypeError is raised.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: A = E.heegner_point(-7,5).ring_class_field() sage: B = E.heegner_point(-7).ring_class_field() sage: C = E.heegner_point(-20).ring_class_field() sage: D = E.heegner_point(-7,15).ring_class_field() sage: B.is_subfield(A) True sage: B.is_subfield(B) True sage: B.is_subfield(D) True sage: B.is_subfield(C) False sage: A.is_subfield(B) False sage: A.is_subfield(D) True """ raise TypeError("M must be a ring class field") M.conductor() % self.conductor() == 0
################################################################################## # # Galois groups of ring class fields # ##################################################################################
class GaloisGroup(SageObject): """ A Galois group of a ring class field.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: G = E.heegner_point(-7,5).ring_class_field().galois_group(); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: G.field() Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: G.cardinality() 12 sage: G.complex_conjugation() Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5
TESTS::
sage: G = heegner_point(37,-7).ring_class_field().galois_group() sage: loads(dumps(G)) == G True sage: type(G) <class 'sage.schemes.elliptic_curves.heegner.GaloisGroup'> """ def __init__(self, field, base=QQ): r""" INPUT:
- ``field`` -- a ring class field
- ``base`` -- subfield of field (default: `\QQ`)
EXAMPLES::
sage: K5 = heegner_points(389,-7,5).ring_class_field() sage: K1 = heegner_points(389,-7,1).ring_class_field() sage: sage.schemes.elliptic_curves.heegner.GaloisGroup(K5,K1) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 over Hilbert class field of QQ[sqrt(-7)] sage: K5.galois_group(K1) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 over Hilbert class field of QQ[sqrt(-7)] """ raise TypeError("field must be of type RingClassField") raise TypeError("base must be of type RingClassField or QQ or quadratic field") raise TypeError("base must be a subfield of field")
def __eq__(self, G): """ EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: G == G True sage: G == 0 False sage: H = EllipticCurve('389a').heegner_point(-7,11).ring_class_field().galois_group() sage: G == H False """
def __ne__(self, other): """ EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: G != G False sage: G != 0 True sage: H = EllipticCurve('389a').heegner_point(-7,11).ring_class_field().galois_group() sage: G != H True """
def __hash__(self): """ Return hash of this Galois group, which is the same as the hash of the pair, the field and its base.
EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: hash(G) == hash((G.field(), G.base_field())) True
"""
def __call__(self, x): """ Coerce `x` into ``self``, where `x` is a Galois group element, or in case ``self`` has base field the Hilbert class field, `x` can also be an element of the ring of integers.
INPUT:
- `x` -- automorphism or quadratic field element
OUTPUT:
- automorphism (or TypeError)
EXAMPLES::
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: G(1) Class field automorphism defined by x^2 + 325*y^2 sage: G(G[0]) Class field automorphism defined by x^2 + 325*y^2 sage: alpha = 2 + K1.quadratic_field().gen(); alpha sqrt_minus_52 + 2 sage: G(alpha) Class field automorphism defined by 14*x^2 - 10*x*y + 25*y^2
A TypeError is raised when the coercion is not possible::
sage: G(0) Traceback (most recent call last): ... TypeError: x does not define element of (O_K/c*O_K)^*
"""
def _repr_(self): """ Return string representation of this Galois group.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: G = E.heegner_point(-7,5).ring_class_field().galois_group() sage: G._repr_() 'Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5' """ else:
def field(self): """ Return the ring class field that this Galois group acts on.
EXAMPLES::
sage: G = heegner_point(389,-7,5).ring_class_field().galois_group() sage: G.field() Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
def base_field(self): """ Return the base field, which the field fixed by all the automorphisms in this Galois group.
EXAMPLES::
sage: x = heegner_point(37,-7,5) sage: Kc = x.ring_class_field(); Kc Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: K = x.quadratic_field() sage: G = Kc.galois_group(); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: G.base_field() Rational Field sage: G.cardinality() 12 sage: Kc.absolute_degree() 12 sage: G = Kc.galois_group(K); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 over Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: G.cardinality() 6 sage: G.base_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: G = Kc.galois_group(Kc); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 over Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: G.cardinality() 1 sage: G.base_field() Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
@cached_method def kolyvagin_generators(self): r""" Assuming this Galois group `G` is of the form `G=\textrm{Gal}(K_c/K_1)`, with `c=p_1\dots p_n` satisfying the Kolyvagin hypothesis, this function returns noncanonical choices of lifts of generators for each of the cyclic factors of `G` corresponding to the primes dividing `c`. Thus the `i`-th returned valued is an element of `G` that maps to the identity element of `\textrm{Gal}(K_p/K_1)` for all `p \neq p_i` and to a choice of generator of `\textrm{Gal}(K_{p_i}/K_1)`.
OUTPUT:
- list of elements of ``self``
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: G.kolyvagin_generators() (Class field automorphism defined by 9*x^2 - 6*x*y + 14*y^2,)
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: G.kolyvagin_generators() (Class field automorphism defined by 17*x^2 - 14*x*y + 22*y^2,) """ raise ValueError("field must be of the form Gal(K_c/K_1)") raise NotImplementedError("only implemented when c is prime")
# Since c satisfies Kolyvagin and is prime, the group is cyclic, # so we just find a generator.
raise NotImplementedError
@cached_method def lift_of_hilbert_class_field_galois_group(self): r""" Assuming this Galois group `G` is of the form `G=\textrm{Gal}(K_c/K)`, this function returns noncanonical choices of lifts of the elements of the quotient group `\textrm{Gal}(K_1/K)`.
OUTPUT:
- tuple of elements of self
EXAMPLES::
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: G = K5.galois_group(K5.quadratic_field()) sage: G.lift_of_hilbert_class_field_galois_group() (Class field automorphism defined by x^2 + 325*y^2, Class field automorphism defined by 2*x^2 + 2*x*y + 163*y^2) sage: G.cardinality() 12 sage: K5.quadratic_field().class_number() 2 """ raise ValueError("Galois group must be of the form Gal(K_c/K)")
@cached_method def _list(self): r""" Enumerate the elements of ``self``.
EXAMPLES::
Example with order 1 (a special case)::
sage: E = EllipticCurve('389a'); F= E.heegner_point(-7,1).ring_class_field() sage: G = F.galois_group(F.quadratic_field()) sage: G._list() (Class field automorphism defined by x^2 + x*y + 2*y^2,)
Example over quadratic imaginary field::
sage: E = EllipticCurve('389a'); F= E.heegner_point(-7,5).ring_class_field() sage: G = F.galois_group(F.quadratic_field()) sage: G._list() (Class field automorphism defined by x^2 + x*y + 44*y^2, Class field automorphism defined by 2*x^2 - x*y + 22*y^2, Class field automorphism defined by 2*x^2 + x*y + 22*y^2, Class field automorphism defined by 4*x^2 - x*y + 11*y^2, Class field automorphism defined by 4*x^2 + x*y + 11*y^2, Class field automorphism defined by 7*x^2 + 7*x*y + 8*y^2)
Example over `\QQ` (it is not implemented yet)::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K3.galois_group()._list() Traceback (most recent call last): ... NotImplementedError: Galois group over QQ not yet implemented
Example over Hilbert class field::
sage: K3 = heegner_points(389,-52,3).ring_class_field(); K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: G._list() (Class field automorphism defined by x^2 + 117*y^2, Class field automorphism defined by 9*x^2 - 6*x*y + 14*y^2, Class field automorphism defined by 9*x^2 + 13*y^2, Class field automorphism defined by 9*x^2 + 6*x*y + 14*y^2) """ # Over the quadratic imaginary field, so straightforward # enumeration of all reduced primitive binary quadratic # forms of discriminant D*c^2.
# Take only the automorphisms in the quad imag case that map to # a principal ideal. # sigma does define an element of our Galois subgroup. else: raise NotImplementedError("general Galois group not yet implemented")
def _quadratic_form_to_alpha(self, f): """ INPUT:
- `f` -- a binary quadratic form with discriminant `c^2 D`
OUTPUT:
- an element of the ring of integers of the quadratic imaginary field
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field(); K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: [G._quadratic_form_to_alpha(s.quadratic_form()) for s in G] [3/2*sqrt_minus_52, 1/6*sqrt_minus_52 + 1/3, 1/6*sqrt_minus_52, 1/6*sqrt_minus_52 - 1/3]
What happens when we input a quadratic form that has nothing to do with `G`::
sage: G._quadratic_form_to_alpha(BinaryQF([1,2,3])) Traceback (most recent call last): ... ValueError: quadratic form has the wrong discriminant """
def _alpha_to_automorphism(self, alpha): r""" Assuming ``self`` has base field the Hilbert class field, make an automorphism from the element `\alpha` of the ring of integers into ``self``.
INPUT:
- `\alpha` -- element of quadratic imaginary field coprime to conductor
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: G._alpha_to_automorphism(1) Class field automorphism defined by x^2 + 117*y^2 sage: [G._alpha_to_automorphism(s.alpha()) for s in G] == list(G) True """ raise TypeError("base must be Hilbert class field with Kolyvagin condition on conductor")
def _alpha_to_p1_element(self, alpha): r""" Given an element of the ring of integers that is nonzero modulo c, return canonical (after our fixed choice of basis) element of the project line corresponding to it.
INPUT:
- `\alpha` -- element of the ring of integers of the quadratic imaginary field
OUTPUT:
- 2-tuple of integers
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: G._alpha_to_p1_element(1) (1, 0) sage: sorted([G._alpha_to_p1_element(s.alpha()) for s in G]) [(0, 1), (1, 0), (1, 1), (1, 2)] """ # todo (optimize) -- this whole function can be massively optimized: w = (1,0)
def _p1_element_to_alpha(self, uv): """ Convert a normalized pair ``uv=(u,v)`` of integers to the corresponding element of the ring of integers got by taking `u b_0 + v b_1` where `b_0, b_1` are the basis for the ring of integers.
INPUT:
- ``uv`` -- pair of integers
OUTPUT:
- element of maximal order of quadratic field
EXAMPLES::
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: v = [G._alpha_to_p1_element(s.alpha()) for s in G] sage: [G._p1_element_to_alpha(z) for z in v] [1, 1/2*sqrt_minus_52, 1/2*sqrt_minus_52 + 1, 2*sqrt_minus_52 + 1, sqrt_minus_52 + 1, 3/2*sqrt_minus_52 + 1] sage: [G(G._p1_element_to_alpha(z)) for z in v] == list(G) True """
def _base_is_QQ(self): r""" Return ``True`` if the base field of this ring class field is `\QQ`.
EXAMPLES::
sage: H = heegner_points(389,-20,3); M = H.ring_class_field() sage: M.galois_group(H.quadratic_field())._base_is_QQ() False sage: M.galois_group(QQ)._base_is_QQ() True sage: M.galois_group(heegner_points(389,-20,1).ring_class_field())._base_is_QQ() False """
def _base_is_quad_imag_field(self): """ Return ``True`` if the base field of this ring class field is the quadratic imaginary field `K`.
EXAMPLES::
sage: H = heegner_points(389,-20,3); M = H.ring_class_field() sage: M.galois_group(H.quadratic_field())._base_is_quad_imag_field() True sage: M.galois_group(QQ)._base_is_quad_imag_field() False sage: M.galois_group(heegner_points(389,-20,1).ring_class_field())._base_is_quad_imag_field() False """
def is_kolyvagin(self): """ Return ``True`` if conductor `c` is prime to the discriminant of the quadratic field, `c` is squarefree and each prime dividing `c` is inert.
EXAMPLES::
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: K5.galois_group(K1).is_kolyvagin() True sage: K7 = heegner_points(389,-52,7).ring_class_field() sage: K7.galois_group(K1).is_kolyvagin() False sage: K25 = heegner_points(389,-52,25).ring_class_field() sage: K25.galois_group(K1).is_kolyvagin() False """
def _base_is_hilbert_class_field(self): """ Return ``True`` if the base field of this ring class field is the Hilbert class field of `K` viewed as a ring class field (so not of data type QuadraticField).
EXAMPLES::
sage: H = heegner_points(389,-20,3); M = H.ring_class_field() sage: M.galois_group(H.quadratic_field())._base_is_hilbert_class_field() False sage: M.galois_group(QQ)._base_is_hilbert_class_field() False sage: M.galois_group(heegner_points(389,-20,1).ring_class_field())._base_is_hilbert_class_field() True """
def __getitem__(self, i): """ EXAMPLES::
sage: E = EllipticCurve('389a'); F= E.heegner_point(-7,5).ring_class_field() sage: G = F.galois_group(F.quadratic_field()) sage: G[0] Class field automorphism defined by x^2 + x*y + 44*y^2 """
def __len__(self): """ EXAMPLES::
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: G.cardinality() 6 sage: len(G) 6 """
@cached_method def cardinality(self): """ Return the cardinality of this Galois group.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: G = E.heegner_point(-7,5).ring_class_field().galois_group(); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: G.cardinality() 12 sage: G = E.heegner_point(-7).ring_class_field().galois_group() sage: G.cardinality() 2 sage: G = E.heegner_point(-7,55).ring_class_field().galois_group() sage: G.cardinality() 120 """
@cached_method def complex_conjugation(self): """ Return the automorphism of ``self`` determined by complex conjugation. The base field must be the rational numbers.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: G = E.heegner_point(-7,5).ring_class_field().galois_group() sage: G.complex_conjugation() Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5 """ raise ValueError("the base field must be fixed by complex conjugation")
################################################################################## # # Elements of Galois groups # ##################################################################################
class GaloisAutomorphism(SageObject): """ An abstract automorphism of a ring class field.
.. TODO::
make :class:`GaloisAutomorphism` derive from GroupElement, so that one gets powers for free, etc. """ def __init__(self, parent): """ INPUT:
- ``parent`` -- a group of automorphisms of a ring class field
EXAMPLES::
sage: G = heegner_points(389,-7,5).ring_class_field().galois_group(); G Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: sage.schemes.elliptic_curves.heegner.GaloisAutomorphism(G) <sage.schemes.elliptic_curves.heegner.GaloisAutomorphism object at ...> """
def parent(self): """ Return the parent of this automorphism, which is a Galois group of a ring class field.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: s = E.heegner_point(-7,5).ring_class_field().galois_group().complex_conjugation() sage: s.parent() Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
def domain(self): """ Return the domain of this automorphism.
EXAMPLES::
sage: E = EllipticCurve('389a') sage: s = E.heegner_point(-7,5).ring_class_field().galois_group().complex_conjugation() sage: s.domain() Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
class GaloisAutomorphismComplexConjugation(GaloisAutomorphism): """ The complex conjugation automorphism of a ring class field.
EXAMPLES::
sage: conj = heegner_point(37,-7,5).ring_class_field().galois_group().complex_conjugation() sage: conj Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5 sage: conj.domain() Ring class field extension of QQ[sqrt(-7)] of conductor 5
TESTS::
sage: type(conj) <class 'sage.schemes.elliptic_curves.heegner.GaloisAutomorphismComplexConjugation'> sage: loads(dumps(conj)) == conj True """ def __init__(self, parent): """ INPUT:
- ``parent`` -- a group of automorphisms of a ring class field
EXAMPLES::
sage: G = heegner_point(37,-7,5).ring_class_field().galois_group() sage: sage.schemes.elliptic_curves.heegner.GaloisAutomorphismComplexConjugation(G) Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
def __hash__(self): """ The hash value is the same as the hash value of the pair ``(self.parent(), 1)``.
EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: conj = G.complex_conjugation() sage: hash(conj) == hash((conj.parent(), 1)) True """
def __eq__(self, right): """ EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: conj = G.complex_conjugation() sage: conj2 = sage.schemes.elliptic_curves.heegner.GaloisAutomorphismComplexConjugation(G) sage: conj is conj2 False sage: conj == conj2 True """ self.parent() == right.parent()
def __ne__(self, other): """ EXAMPLES::
sage: G = EllipticCurve('389a').heegner_point(-7,5).ring_class_field().galois_group() sage: conj = G.complex_conjugation() sage: conj2 = sage.schemes.elliptic_curves.heegner.GaloisAutomorphismComplexConjugation(G) sage: conj != conj2 False """
def _repr_(self): """ Return print representation of the complex conjugation automorphism.
EXAMPLES::
sage: conj = heegner_point(37,-7,5).ring_class_field().galois_group().complex_conjugation() sage: conj._repr_() 'Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5' """
## def __mul__(self, right): ## """ ## Return the composition of two automorphisms.
## EXAMPLES::
## sage: ? ## """ ## if self.parent() != right.__parent(): ## raise TypeError, "automorphisms must be of the same class field" ## raise NotImplementedError
def __invert__(self): """ Return the inverse of ``self``, which is just ``self`` again.
EXAMPLES::
sage: conj = heegner_point(37,-7,5).ring_class_field().galois_group().complex_conjugation() sage: ~conj Complex conjugation automorphism of Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
def order(self): """ EXAMPLES::
sage: conj = heegner_point(37,-7,5).ring_class_field().galois_group().complex_conjugation() sage: conj.order() 2 """
@richcmp_method class GaloisAutomorphismQuadraticForm(GaloisAutomorphism): """ An automorphism of a ring class field defined by a quadratic form.
EXAMPLES::
sage: H = heegner_points(389,-20,3) sage: sigma = H.ring_class_field().galois_group(H.quadratic_field())[0]; sigma Class field automorphism defined by x^2 + 45*y^2 sage: type(sigma) <class 'sage.schemes.elliptic_curves.heegner.GaloisAutomorphismQuadraticForm'> sage: loads(dumps(sigma)) == sigma True """ def __init__(self, parent, quadratic_form, alpha=None): r""" INPUT:
- ``parent`` -- a group of automorphisms of a ring class field
- ``quadratic_form`` -- a binary quadratic form that defines an element of the Galois group of `K_c` over `K`.
- ``\alpha`` -- (default: ``None``) optional data that specified element corresponding element of `(\mathcal{O}_K / c\mathcal{O}_K)^* / (\ZZ/c\ZZ)^*`, via class field theory.
EXAMPLES::
sage: H = heegner_points(389,-20,3); G = H.ring_class_field().galois_group(H.quadratic_field()) sage: f = BinaryQF_reduced_representatives(-20*9)[0] sage: sage.schemes.elliptic_curves.heegner.GaloisAutomorphismQuadraticForm(G, f) Class field automorphism defined by x^2 + 45*y^2 """
@cached_method def order(self): """ Return the multiplicative order of this Galois group automorphism.
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: sorted([g.order() for g in G]) [1, 2, 4, 4] sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: sorted([g.order() for g in G]) [1, 2, 3, 3, 6, 6] """ raise NotImplementedError("order only currently implemented when alpha given in construction") assert False, "bug in order"
def alpha(self): r""" Optional data that specified element corresponding element of `(\mathcal{O}_K / c\mathcal{O}_K)^* / (\ZZ/c\ZZ)^*`, via class field theory.
This is a generator of the ideal corresponding to this automorphism.
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: orb = sorted([g.alpha() for g in G]); orb # random (the sign depends on the database being installed or not) [1, 1/2*sqrt_minus_52 + 1, -1/2*sqrt_minus_52, 1/2*sqrt_minus_52 - 1] sage: sorted([x^2 for x in orb]) # this is just for testing [-13, -sqrt_minus_52 - 12, sqrt_minus_52 - 12, 1]
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: orb = sorted([g.alpha() for g in G]); orb # random (the sign depends on the database being installed or not) [1, -1/2*sqrt_minus_52, 1/2*sqrt_minus_52 + 1, 1/2*sqrt_minus_52 - 1, 1/2*sqrt_minus_52 - 2, -1/2*sqrt_minus_52 - 2] sage: sorted([x^2 for x in orb]) # just for testing [-13, -sqrt_minus_52 - 12, sqrt_minus_52 - 12, -2*sqrt_minus_52 - 9, 2*sqrt_minus_52 - 9, 1]
""" raise ValueError("alpha data not defined")
@cached_method def p1_element(self): r""" Return element of the projective line corresponding to this automorphism.
This only makes sense if this automorphism is in the Galois group `\textrm{Gal}(K_c/K_1)`.
EXAMPLES::
sage: K3 = heegner_points(389,-52,3).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K3.galois_group(K1) sage: sorted([g.p1_element() for g in G]) [(0, 1), (1, 0), (1, 1), (1, 2)]
sage: K5 = heegner_points(389,-52,5).ring_class_field() sage: K1 = heegner_points(389,-52,1).ring_class_field() sage: G = K5.galois_group(K1) sage: sorted([g.p1_element() for g in G]) [(0, 1), (1, 0), (1, 1), (1, 2), (1, 3), (1, 4)] """
def __hash__(self): """ The hash value is the hash of the pair formed by the parent and the quadratic form read as tuple.
EXAMPLES::
sage: H = heegner_points(389,-20,3) sage: s = H.ring_class_field().galois_group(H.quadratic_field())[0] sage: hash(s) == hash((s.parent(), tuple(s.quadratic_form()))) True """
def __richcmp__(self, right, op): """ Comparison.
EXAMPLES::
sage: H = heegner_points(389,-7,5) sage: s = H.ring_class_field().galois_group(H.quadratic_field())[1] sage: s == s True sage: s == s*s False sage: s == s*s*s*s*s False sage: s == s*s*s*s*s*s*s True
sage: H = heegner_points(389,-20,3) sage: s = H.ring_class_field().galois_group(H.quadratic_field())[0] sage: s == s True sage: s == 0 False """ return richcmp_not_equal(lx, rx, op)
def _repr_(self): """ Return string representation of this automorphism.
EXAMPLES::
sage: H = heegner_points(389,-20,3); s = H.ring_class_field().galois_group(H.quadratic_field())[0] sage: s._repr_() 'Class field automorphism defined by x^2 + 45*y^2'
"""
def __mul__(self, right): """ Return the composition of two automorphisms.
EXAMPLES::
sage: H = heegner_points(389,-20,3); s = H.ring_class_field().galois_group(H.quadratic_field())[0] sage: s * s Class field automorphism defined by x^2 + 45*y^2 sage: G = s.parent(); list(G) [Class field automorphism defined by x^2 + 45*y^2, Class field automorphism defined by 2*x^2 + 2*x*y + 23*y^2, Class field automorphism defined by 5*x^2 + 9*y^2, Class field automorphism defined by 7*x^2 + 4*x*y + 7*y^2] sage: G[0]*G[0] Class field automorphism defined by x^2 + 45*y^2 sage: G[1]*G[2] == G[3] True """ raise TypeError("automorphisms must be of the same class field") # TODO: special case when right is complex conjugation raise NotImplementedError alpha = self.__alpha * right.__alpha else:
def quadratic_form(self): """ Return reduced quadratic form corresponding to this Galois automorphism.
EXAMPLES::
sage: H = heegner_points(389,-20,3); s = H.ring_class_field().galois_group(H.quadratic_field())[0] sage: s.quadratic_form() x^2 + 45*y^2 """
@cached_method def ideal(self): r""" Return ideal of ring of integers of quadratic imaginary field corresponding to this quadratic form. This is the ideal
`I = \left(A, \frac{-B+ c\sqrt{D}}{2}\right) \mathcal{O}_K`.
EXAMPLES::
sage: E = EllipticCurve('389a'); F= E.heegner_point(-20,3).ring_class_field() sage: G = F.galois_group(F.quadratic_field()) sage: G[1].ideal() Fractional ideal (2, 1/2*sqrt_minus_20 + 1) sage: [s.ideal().gens() for s in G] [(1, 3/2*sqrt_minus_20), (2, 3/2*sqrt_minus_20 - 1), (5, 3/2*sqrt_minus_20), (7, 3/2*sqrt_minus_20 - 2)] """
## def __call__(self, z): ## """ ## Return image of the Heegner point `z` under this automorphism. ## ## INPUT: ## ## - `z` -- a Heegner point on `X_0(N)` or an elliptic curve ## ## OUTPUT: ## ## - a Heegner point ## ## EXAMPLES:: ## ## sage: x = heegner_point(389,-20,3); F = x.ring_class_field() ## sage: sigma = F.galois_group(F.quadratic_field())[1]; sigma ## Class field automorphism defined by 2*x^2 + 2*x*y + 23*y^2 ## sage: sigma(x) ## Heegner point 3/1556*sqrt(-20) - 495/778 of discriminant -20 and conductor 3 on X_0(389) ## """ ## if isinstance(z, HeegnerPointOnX0N): ## if z.ring_class_field() != self.domain(): ## raise NotImplementedError, "class fields must be the same" ## # TODO -- check more compatibilities? ## # TODO -- this is surely backwards -- something must be inverted? ## f = z.quadratic_form() * self.quadratic_form() ## # TODO -- put f into the correct form with A divisible by N, etc.? ## # That could be done by looking up reduced form of f in a canonical ## # list of best reps. ## N,D,c = z.level(),z.discriminant(),z.conductor() ## return HeegnerPointOnX0N(N,D,c, f = f) ## else: ## raise NotImplementedError
################################################################################## # # Specific Heegner points # ##################################################################################
@richcmp_method class HeegnerPoint(SageObject): r""" A Heegner point of level `N`, discriminant `D` and conductor `c` is any point on a modular curve or elliptic curve that is concocted in some way from a quadratic imaginary `\tau` in the upper half plane with `\Delta(\tau) = D c = \Delta(N \tau)`.
EXAMPLES::
sage: x = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,13); x Heegner point of level 389, discriminant -7, and conductor 13 sage: type(x) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoint'> sage: loads(dumps(x)) == x True """ def __init__(self, N, D, c): """ INPUT:
- `N` -- (positive integer) the level
- `D` -- (negative integer) fundamental discriminant
- `c` -- (positive integer) conductor
Since this is an abstract base class, no type or compatibility checks are done, as those are all assumed to be done in the derived class.
EXAMPLES::
sage: H = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,5) sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoint'> """
def __richcmp__(self, x, op): """ Compare two Heegner points.
EXAMPLES::
sage: H = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,5) sage: H == H True
sage: H = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,5); type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoint'> sage: J = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,11) sage: H == H True sage: H == J False sage: J == H False sage: H == 0 False """ (x.__N, x.__D, x.__c), op)
def _repr_(self): """ EXAMPLES::
sage: H = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,5) sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoint'> sage: H._repr_() 'Heegner point of level 389, discriminant -7, and conductor 5' """ self.__N, self.__D, self.__c)
def __hash__(self): """ The hash value is obtained from level, discriminant, and conductor.
EXAMPLES::
sage: H = sage.schemes.elliptic_curves.heegner.HeegnerPoint(389,-7,5); type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoint'> sage: hash(H) == hash((H.level(), H.discriminant(), H.conductor())) True """
def level(self): """ Return the level of this Heegner point, which is the level of the modular curve `X_0(N)` on which this is a Heegner point.
EXAMPLES::
sage: heegner_point(389,-7,5).level() 389 """
def conductor(self): """ Return the conductor of this Heegner point.
EXAMPLES::
sage: heegner_point(389,-7,5).conductor() 5 sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67,7); P Kolyvagin point of discriminant -67 and conductor 7 on elliptic curve of conductor 37 sage: P.conductor() 7 sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P.conductor() 5 """
def discriminant(self): """ Return the discriminant of the quadratic imaginary field associated to this Heegner point.
EXAMPLES::
sage: heegner_point(389,-7,5).discriminant() -7 sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67,7); P Kolyvagin point of discriminant -67 and conductor 7 on elliptic curve of conductor 37 sage: P.discriminant() -67 sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P.discriminant() -7 """
@cached_method def quadratic_field(self): """ Return the quadratic number field of discriminant `D`.
EXAMPLES::
sage: x = heegner_point(37,-7,5) sage: x.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7
sage: E = EllipticCurve('37a'); P = E.heegner_point(-40) sage: P.quadratic_field() Number Field in sqrt_minus_40 with defining polynomial x^2 + 40 sage: P.quadratic_field() is P.quadratic_field() True sage: type(P.quadratic_field()) <class 'sage.rings.number_field.number_field.NumberField_quadratic_with_category'> """
@cached_method def quadratic_order(self): """ Return the order in the quadratic imaginary field of conductor `c`, where `c` is the conductor of this Heegner point.
EXAMPLES::
sage: heegner_point(389,-7,5).quadratic_order() Order in Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: heegner_point(389,-7,5).quadratic_order().basis() [1, 5*sqrt_minus_7]
sage: E = EllipticCurve('37a'); P = E.heegner_point(-40,11) sage: P.quadratic_order() Order in Number Field in sqrt_minus_40 with defining polynomial x^2 + 40 sage: P.quadratic_order().basis() [1, 11*sqrt_minus_40]
"""
@cached_method def ring_class_field(self): """ Return the ring class field associated to this Heegner point. This is an extension `K_c` over `K`, where `K` is the quadratic imaginary field and `c` is the conductor associated to this Heegner point. This Heegner point is defined over `K_c` and the Galois group `Gal(K_c/K)` acts transitively on the Galois conjugates of this Heegner point.
EXAMPLES::
sage: E = EllipticCurve('389a'); K.<a> = QuadraticField(-5) sage: len(K.factor(5)) 1 sage: len(K.factor(23)) 2 sage: E.heegner_point(-7, 5).ring_class_field().degree_over_K() 6 sage: E.heegner_point(-7, 23).ring_class_field().degree_over_K() 22 sage: E.heegner_point(-7, 5*23).ring_class_field().degree_over_K() 132 sage: E.heegner_point(-7, 5^2).ring_class_field().degree_over_K() 30 sage: E.heegner_point(-7, 7).ring_class_field().degree_over_K() 7 """
################################################################################## # # Sets of Heegner points # ##################################################################################
class HeegnerPoints(SageObject): """ The set of Heegner points with given parameters.
EXAMPLES::
sage: H = heegner_points(389); H Set of all Heegner points on X_0(389) sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoints_level'> sage: isinstance(H, sage.schemes.elliptic_curves.heegner.HeegnerPoints) True """ def __init__(self, N): """ INPUT:
- `N` -- level, a positive integer
EXAMPLES::
sage: heegner_points(37) Set of all Heegner points on X_0(37) sage: heegner_points(0) Traceback (most recent call last): ... ValueError: N must a positive integer """
def level(self): """ Return the level `N` of the modular curve `X_0(N)`.
EXAMPLES::
sage: heegner_points(389).level() 389 """
class HeegnerPoints_level(HeegnerPoints): """ Return the infinite set of all Heegner points on `X_0(N)` for all quadratic imaginary fields.
EXAMPLES::
sage: H = heegner_points(11); H Set of all Heegner points on X_0(11) sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoints_level'> sage: loads(dumps(H)) == H True """ def __eq__(self, other): """ EXAMPLES::
sage: H = heegner_points(11) sage: H == heegner_points(13) False sage: H == heegner_points(11) True sage: H == 0 False """
def __ne__(self, other): """ EXAMPLES::
sage: H = heegner_points(11) sage: H != heegner_points(13) True sage: H != heegner_points(11) False sage: H != 0 True """
def _repr_(self): """ Return string representation of the set of Heegner points.
EXAMPLES::
sage: heegner_points(389)._repr_() 'Set of all Heegner points on X_0(389)' """
def reduce_mod(self, ell): r""" Return object that allows for computation with Heegner points of level `N` modulo the prime `\ell`, represented using quaternion algebras.
INPUT:
- `\ell` -- prime
EXAMPLES::
sage: heegner_points(389).reduce_mod(7).quaternion_algebra() Quaternion Algebra (-1, -7) with base ring Rational Field """
def discriminants(self, n=10, weak=False): r""" Return the first `n` quadratic imaginary discriminants that satisfy the Heegner hypothesis for `N`.
INPUT:
- `n` -- nonnegative integer
- ``weak`` -- bool (default: ``False``); if ``True`` only require weak Heegner hypothesis, which is the same as usual but without the condition that `\gcd(D,N)=1`.
EXAMPLES::
sage: X = heegner_points(37) sage: X.discriminants(5) [-7, -11, -40, -47, -67]
The default is 10::
sage: X.discriminants() [-7, -11, -40, -47, -67, -71, -83, -84, -95, -104] sage: X.discriminants(15) [-7, -11, -40, -47, -67, -71, -83, -84, -95, -104, -107, -115, -120, -123, -127]
The discriminant -111 satisfies only the weak Heegner hypothesis, since it is divisible by 37::
sage: X.discriminants(15,weak=True) [-7, -11, -40, -47, -67, -71, -83, -84, -95, -104, -107, -111, -115, -120, -123] """ # if not weak, then also require gcd(D,N)=1
class HeegnerPoints_level_disc(HeegnerPoints): """ Set of Heegner points of given level and all conductors associated to a quadratic imaginary field.
EXAMPLES::
sage: H = heegner_points(389,-7); H Set of all Heegner points on X_0(389) associated to QQ[sqrt(-7)] sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoints_level_disc'> sage: H._repr_() 'Set of all Heegner points on X_0(389) associated to QQ[sqrt(-7)]' sage: H.discriminant() -7 sage: H.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: H.kolyvagin_conductors() [1, 3, 5, 13, 15, 17, 19, 31, 39, 41]
sage: loads(dumps(H)) == H True """ def __init__(self, N, D): """ INPUT:
- `N` -- positive integer
- `D` -- negative fundamental discriminant
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.HeegnerPoints_level_disc(37,-7) Set of all Heegner points on X_0(37) associated to QQ[sqrt(-7)] """ raise ValueError("D (=%s) must satisfy the weak Heegner hypothesis for N (=%s)"%(D,N))
def __eq__(self, other): """ EXAMPLES::
sage: H = heegner_points(389,-7) sage: H == heegner_points(389,-7) True sage: H == 0 False sage: H == heegner_points(389,-11) False """ self.level() == other.level() and self.__D == other.__D
def __ne__(self, other): """ EXAMPLES::
sage: H = heegner_points(389,-7) sage: H != heegner_points(389,-7) False sage: H != 0 True sage: H != heegner_points(389,-11) True """
def _repr_(self): """ Return string representation of the set of Heegner points for a given quadratic field.
EXAMPLES::
sage: heegner_points(389,-7)._repr_() 'Set of all Heegner points on X_0(389) associated to QQ[sqrt(-7)]' """ self.level(), self.discriminant())
def discriminant(self): r""" Return the discriminant of the quadratic imaginary extension `K`.
EXAMPLES::
sage: heegner_points(389,-7).discriminant() -7 """
@cached_method def quadratic_field(self): r""" Return the quadratic imaginary field `K = \QQ(\sqrt{D})`.
EXAMPLES::
sage: E = EllipticCurve('389a'); K = E.heegner_point(-7,5).ring_class_field() sage: K.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 """
def kolyvagin_conductors(self, r=None, n=10, E=None, m=None): r""" Return the first `n` conductors that are squarefree products of distinct primes inert in the quadratic imaginary field `K = \QQ(\sqrt{D})`. If `r` is specified, return only conductors that are a product of `r` distinct primes all inert in `K`. If `r = 0`, always return the list ``[1]``, no matter what.
If the optional elliptic curve `E` and integer `m` are given, then only include conductors `c` such that for each prime divisor `p` of `c` we have `m \mid \gcd(a_p(E), p+1)`.
INPUT:
- `r` -- (default: ``None``) nonnegative integer or ``None``
- `n` -- positive integer
- `E` -- an elliptic curve
- `m` -- a positive integer
EXAMPLES::
sage: H = heegner_points(389,-7) sage: H.kolyvagin_conductors(0) [1] sage: H.kolyvagin_conductors(1) [3, 5, 13, 17, 19, 31, 41, 47, 59, 61] sage: H.kolyvagin_conductors(1,15) [3, 5, 13, 17, 19, 31, 41, 47, 59, 61, 73, 83, 89, 97, 101] sage: H.kolyvagin_conductors(1,5) [3, 5, 13, 17, 19] sage: H.kolyvagin_conductors(1,5,EllipticCurve('389a'),3) [5, 17, 41, 59, 83] sage: H.kolyvagin_conductors(2,5,EllipticCurve('389a'),3) [85, 205, 295, 415, 697] """ raise ValueError("D must satisfy the weak Heegner hypothesis") raise ValueError("n must be a positive integer") raise ValueError("n must be a nonnegative integer")
def is_kolyvagin_conductor(N, E, D, r, n, c): r""" Return ``True`` if `c` is a Kolyvagin conductor for level `N`, discriminant `D`, mod `n`, etc., i.e., `c` is divisible by exactly `r` prime factors, is coprime to `ND`, each prime dividing `c` is inert, and if `E` is not ``None`` then `n | \gcd(p+1, a_p(E))` for each prime `p` dividing `c`.
INPUT:
- `N` -- level (positive integer)
- `E` -- elliptic curve or ``None``
- `D` -- negative fundamental discriminant
- `r` -- number of prime factors (nonnegative integer) or ``None``
- `n` -- torsion order (i.e., do we get class in `(E(K_c)/n E(K_c))^{Gal(K_c/K)}`?)
- `c` -- conductor (positive integer)
EXAMPLES::
sage: from sage.schemes.elliptic_curves.heegner import is_kolyvagin_conductor sage: is_kolyvagin_conductor(389,None,-7,1,None,5) True sage: is_kolyvagin_conductor(389,None,-7,1,None,7) False sage: is_kolyvagin_conductor(389,None,-7,1,None,11) False sage: is_kolyvagin_conductor(389,EllipticCurve('389a'),-7,1,3,5) True sage: is_kolyvagin_conductor(389,EllipticCurve('389a'),-7,1,11,5) False """ # check that each prime in P is inert in K
class HeegnerPoints_level_disc_cond(HeegnerPoints_level, HeegnerPoints_level_disc): """ The set of Heegner points of given level, discriminant, and conductor.
EXAMPLES::
sage: H = heegner_points(389,-7,5); H All Heegner points of conductor 5 on X_0(389) associated to QQ[sqrt(-7)] sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoints_level_disc_cond'> sage: H.discriminant() -7 sage: H.level() 389
sage: len(H.points()) 12 sage: H.points()[0] Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) sage: H.betas() (147, 631)
sage: H.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: H.ring_class_field() Ring class field extension of QQ[sqrt(-7)] of conductor 5
sage: H.kolyvagin_conductors() [1, 3, 5, 13, 15, 17, 19, 31, 39, 41] sage: H.satisfies_kolyvagin_hypothesis() True
sage: H = heegner_points(389,-7,5) sage: loads(dumps(H)) == H True """ def __init__(self, N, D, c=ZZ(1)): """ Create set of Heegner points.
INPUT:
- `N` -- positive integer (the level)
- `D` -- negative fundamental discriminant
- `c` -- conductor (default: 1)
EXAMPLES::
sage: H = heegner_points(389,-7,5); H All Heegner points of conductor 5 on X_0(389) associated to QQ[sqrt(-7)] sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPoints_level_disc_cond'> """
def __eq__(self, other): """ EXAMPLES::
sage: H = heegner_points(389,-7, 3) sage: H == heegner_points(389,-7, 3) True sage: H == heegner_points(389,-7, 1) False sage: H == 0 False """ self.level() == other.level() and self.discriminant() == other.discriminant() \ and self.conductor() == other.conductor()
def __ne__(self, other): """ EXAMPLES::
sage: H = heegner_points(389,-7, 3) sage: H != heegner_points(389,-7, 3) False sage: H != heegner_points(389,-7, 1) True sage: H != 0 True """
def _repr_(self): """ Return string representation of this set of Heegner points.
EXAMPLES::
sage: H = heegner_points(37,-7,5); H._repr_() 'All Heegner points of conductor 5 on X_0(37) associated to QQ[sqrt(-7)]' """ self.conductor(), self.level(), self.discriminant())
def conductor(self): """ Return the level of the conductor.
EXAMPLES::
sage: heegner_points(389,-7,5).conductor() 5 """
@cached_method def satisfies_kolyvagin_hypothesis(self): """ Return ``True`` if ``self`` satisfies the Kolyvagin hypothesis, i.e., that each prime dividing the conductor `c` of ``self`` is inert in `K` and coprime to `ND`.
EXAMPLES:
The prime 5 is inert, but the prime 11 is not::
sage: heegner_points(389,-7,5).satisfies_kolyvagin_hypothesis() True sage: heegner_points(389,-7,11).satisfies_kolyvagin_hypothesis() False """ r=None, n=None, c=self.conductor())
@cached_method def ring_class_field(self): """ Return the ring class field associated to this set of Heegner points. This is an extension `K_c` over `K`, where `K` is the quadratic imaginary field and `c` the conductor associated to this Heegner point. This Heegner point is defined over `K_c` and the Galois group `Gal(K_c/K)` acts transitively on the Galois conjugates of this Heegner point.
EXAMPLES::
sage: heegner_points(389,-7,5).ring_class_field() Ring class field extension of QQ[sqrt(-7)] of conductor 5 """
def __getitem__(self, i): """ Return the `i`-th Heegner point.
EXAMPLES::
sage: H = heegner_points(389,-7,5) sage: len(H) 12 sage: H[0] Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) sage: H[-1] Heegner point 5/5446*sqrt(-7) - 757/778 of discriminant -7 and conductor 5 on X_0(389) """
def __len__(self): """ Return the number of Heegner points.
EXAMPLES::
sage: len(heegner_points(389,-7,5)) 12
When the conductor is 1 the length is a power of 2 (number of square roots of `D` mod `4N` reduced mod `2N`) times the class number::
sage: len(heegner_points(389,-20,1)) 4 sage: QQ[sqrt(-20)].class_number() 2 """
@cached_method def betas(self): """ Return the square roots of `D c^2` modulo `4 N` all reduced mod `2 N`, without multiplicity.
EXAMPLES::
sage: X = heegner_points(45,-11,1); X All Heegner points of conductor 1 on X_0(45) associated to QQ[sqrt(-11)] sage: [x.quadratic_form() for x in X] [45*x^2 + 13*x*y + y^2, 45*x^2 + 23*x*y + 3*y^2, 45*x^2 + 67*x*y + 25*y^2, 45*x^2 + 77*x*y + 33*y^2] sage: X.betas() (13, 23, 67, 77) sage: X.points(13) (Heegner point 1/90*sqrt(-11) - 13/90 of discriminant -11 on X_0(45),) sage: [x.quadratic_form() for x in X.points(13)] [45*x^2 + 13*x*y + y^2] """
@cached_method def points(self, beta=None): r""" Return the Heegner points in ``self``. If `\beta` is given, return only those Heegner points with given `\beta`, i.e., whose quadratic form has `B` congruent to `\beta` modulo `2 N`.
Use ``self.beta()`` to get a list of betas.
EXAMPLES::
sage: H = heegner_points(389,-7,5); H All Heegner points of conductor 5 on X_0(389) associated to QQ[sqrt(-7)] sage: H.points() (Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389), ..., Heegner point 5/5446*sqrt(-7) - 757/778 of discriminant -7 and conductor 5 on X_0(389)) sage: H.betas() (147, 631) sage: [x.tau() for x in H.points(147)] [5/778*sqrt_minus_7 - 147/778, 5/1556*sqrt_minus_7 - 147/1556, 5/1556*sqrt_minus_7 - 925/1556, 5/3112*sqrt_minus_7 - 1703/3112, 5/3112*sqrt_minus_7 - 2481/3112, 5/5446*sqrt_minus_7 - 21/778]
sage: [x.tau() for x in H.points(631)] [5/778*sqrt_minus_7 - 631/778, 5/1556*sqrt_minus_7 - 631/1556, 5/1556*sqrt_minus_7 - 1409/1556, 5/3112*sqrt_minus_7 - 631/3112, 5/3112*sqrt_minus_7 - 1409/3112, 5/5446*sqrt_minus_7 - 757/778]
The result is cached and is a tuple (since it is immutable)::
sage: H.points() is H.points() True sage: type(H.points()) <... 'tuple'> """
# todo (optimize) -- replace for over all s with for over solution set
def plot(self, *args, **kwds): """ Returns plot of all the representatives in the upper half plane of the Heegner points in this set of Heegner points.
The inputs to this function get passed onto the point command.
EXAMPLES::
sage: heegner_points(389,-7,5).plot(pointsize=50, rgbcolor='red') Graphics object consisting of 12 graphics primitives sage: heegner_points(53,-7,15).plot(pointsize=50, rgbcolor='purple') Graphics object consisting of 48 graphics primitives """
class HeegnerPointOnX0N(HeegnerPoint): r""" A Heegner point as a point on the modular curve `X_0(N)`, which we view as the upper half plane modulo the action of `\Gamma_0(N)`.
EXAMPLES::
sage: x = heegner_point(37,-7,5); x Heegner point 5/74*sqrt(-7) - 11/74 of discriminant -7 and conductor 5 on X_0(37) sage: type(x) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPointOnX0N'> sage: x.level() 37 sage: x.conductor() 5 sage: x.discriminant() -7 sage: x.quadratic_field() Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: x.quadratic_form() 37*x^2 + 11*x*y + 2*y^2 sage: x.quadratic_order() Order in Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 sage: x.tau() 5/74*sqrt_minus_7 - 11/74 sage: loads(dumps(x)) == x True """ def __init__(self, N, D, c=ZZ(1), f=None, check=True): r""" INPUT:
- `N` -- positive integer
- `D` -- fundamental discriminant, a negative integer
- `c` -- conductor, a positive integer coprime to `N`
- `f` -- binary quadratic form, 3-tuple `(A,B,C)` of coefficients of `AX^2 + BXY + CY^2`, or element of quadratic imaginary field `\QQ(\sqrt{D})` in the upper half plan.
- ``check`` -- bool, default: ``True``. should not be used except internally.
EXAMPLES::
sage: x = heegner_point(389, -7, 5); x Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) sage: type(x) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPointOnX0N'> sage: sage.schemes.elliptic_curves.heegner.HeegnerPointOnX0N(389, -7, 5, None, check=False) Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) """ raise ValueError("conductor c (=%s) must be coprime to N (=%s)" % (c, N)) raise ValueError("if f is a tuple, it must have length 3") # convert from BinaryQF f = tuple(f) # tau = number field element raise TypeError("number field element f must have degree 2") else: raise TypeError("f must be a 3-tuple, quadratic form, or element of the upper half plane") raise ValueError("f (=%s) must have discriminant %s"%(f, D*c*c)) # We know that N|A, so A = N is optimal.
def __hash__(self): """ The hash is obtained from the hash provided by :class:`HeegnerPoint`, together with the reduced quadratic form.
EXAMPLES::
sage: x = heegner_point(37,-7,5) sage: from sage.schemes.elliptic_curves.heegner import HeegnerPoint sage: hash(x) == hash( (HeegnerPoint.__hash__(x), x.reduced_quadratic_form()) ) True """
def __richcmp__(self, x, op): """ Compare two Heegner points with character.
EXAMPLES::
sage: x1 = EllipticCurve('389a').heegner_point(-7).heegner_point_on_X0N() sage: x5 = EllipticCurve('389a').heegner_point(-7,5).heegner_point_on_X0N() sage: x1 == x1 True sage: x1 < x5 True sage: x5 > x1 True """ return NotImplemented self.conductor(), self.__f), (x.level(), x.discriminant(), x.conductor(), x.__f), op)
def _repr_(self): """ Return string representation of this Heegner point.
EXAMPLES::
sage: x = heegner_point(37,-7,5); x._repr_() 'Heegner point 5/74*sqrt(-7) - 11/74 of discriminant -7 and conductor 5 on X_0(37)' """
def atkin_lehner_act(self, Q=None): r""" Given an integer Q dividing the level N such that `\gcd(Q, N/Q) = 1`, returns the image of this Heegner point under the Atkin-Lehner operator `W_Q`.
INPUT:
- `Q` -- positive divisor of `N`; if not given, default to `N`
EXAMPLES::
sage: x = heegner_point(389,-7,5) sage: x.atkin_lehner_act() Heegner point 5/199168*sqrt(-7) - 631/199168 of discriminant -7 and conductor 5 on X_0(389)
sage: x = heegner_point(45,D=-11,c=1); x Heegner point 1/90*sqrt(-11) - 13/90 of discriminant -11 on X_0(45) sage: x.atkin_lehner_act(5) Heegner point 1/90*sqrt(-11) + 23/90 of discriminant -11 on X_0(45) sage: y = x.atkin_lehner_act(9); y Heegner point 1/90*sqrt(-11) - 23/90 of discriminant -11 on X_0(45) sage: z = y.atkin_lehner_act(9); z Heegner point 1/90*sqrt(-11) - 13/90 of discriminant -11 on X_0(45) sage: z == x True """ return self # trivial special case raise ValueError("Q must divide N and be coprime to N/Q")
@cached_method def quadratic_form(self): """ Return the integral primitive positive-definite binary quadratic form associated to this Heegner point.
EXAMPLES::
sage: heegner_point(389,-7,5).quadratic_form() 389*x^2 + 147*x*y + 14*y^2 """ # It is good/important that this return a copy, since # BinaryQF's stupidly are mutable and cannot be made immutable. # In particular, they have a stupid reduce method that changes # them in place.
def reduced_quadratic_form(self): """ Return reduced binary quadratic corresponding to this Heegner point.
EXAMPLES::
sage: x = heegner_point(389,-7,5) sage: x.quadratic_form() 389*x^2 + 147*x*y + 14*y^2 sage: x.reduced_quadratic_form() 4*x^2 - x*y + 11*y^2 """
@cached_method def tau(self): """ Return an element ``tau`` in the upper half plane that corresponds to this particular Heegner point.
Actually, ``tau`` is in the quadratic imaginary field K associated to this Heegner point.
EXAMPLES::
sage: x = heegner_point(37,-7,5); tau = x.tau(); tau 5/74*sqrt_minus_7 - 11/74 sage: 37 * tau.minpoly() 37*x^2 + 11*x + 2 sage: x.quadratic_form() 37*x^2 + 11*x*y + 2*y^2 """
def map_to_curve(self, E): """ Return the image of this Heegner point on the elliptic curve `E`, which must also have conductor `N`, where `N` is the level of ``self``.
EXAMPLES::
sage: x = heegner_point(389,-7,5); x Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389) sage: y = x.map_to_curve(EllipticCurve('389a')); y Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: y.curve().cremona_label() '389a1' sage: y.heegner_point_on_X0N() Heegner point 5/778*sqrt(-7) - 147/778 of discriminant -7 and conductor 5 on X_0(389)
You can also directly apply the modular parametrization of the elliptic curve::
sage: x = heegner_point(37,-7); x Heegner point 1/74*sqrt(-7) - 17/74 of discriminant -7 on X_0(37) sage: E = EllipticCurve('37a'); phi = E.modular_parametrization() sage: phi(x) Heegner point of discriminant -7 on elliptic curve of conductor 37 """
@cached_method def galois_orbit_over_K(self): r""" Return the `Gal(K_c/K)`-orbit of this Heegner point.
EXAMPLES::
sage: x = heegner_point(389,-7,3); x Heegner point 3/778*sqrt(-7) - 223/778 of discriminant -7 and conductor 3 on X_0(389) sage: x.galois_orbit_over_K() [Heegner point 3/778*sqrt(-7) - 223/778 of discriminant -7 and conductor 3 on X_0(389), Heegner point 3/1556*sqrt(-7) - 223/1556 of discriminant -7 and conductor 3 on X_0(389), Heegner point 3/1556*sqrt(-7) - 1001/1556 of discriminant -7 and conductor 3 on X_0(389), Heegner point 3/3112*sqrt(-7) - 223/3112 of discriminant -7 and conductor 3 on X_0(389)] """
# todo (optimize) -- replace for over all s with for over solution set
def plot(self, **kwds): r""" Draw a point at `(x,y)` where this Heegner point is represented by the point `\tau = x + i y` in the upper half plane.
The ``kwds`` get passed onto the point plotting command.
EXAMPLES::
sage: heegner_point(389,-7,1).plot(pointsize=50) Graphics object consisting of 1 graphics primitive """
class HeegnerPointOnEllipticCurve(HeegnerPoint): """ A Heegner point on a curve associated to an order in a quadratic imaginary field.
EXAMPLES::
sage: E = EllipticCurve('37a'); P = E.heegner_point(-7,5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 37 sage: type(P) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPointOnEllipticCurve'> """ def __init__(self, E, x, check=True): r""" INPUT:
- `E` -- an elliptic curve over the rational numbers
- `x` -- Heegner point on `X_0(N)`
- ``check`` -- bool (default: ``True``); if ``True``, ensure that `D`, `c` are of type Integer and define a Heegner point on `E`
EXAMPLES::
sage: x = heegner_point(389,-7,5) sage: E = EllipticCurve('389a') sage: sage.schemes.elliptic_curves.heegner.HeegnerPointOnEllipticCurve(E, x) Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 """ raise ValueError("conductor of curve must equal level of Heegner point")
@cached_method def satisfies_kolyvagin_hypothesis(self, n=None): """ Return ``True`` if this Heegner point and `n` satisfy the Kolyvagin hypothesis, i.e., that each prime dividing the conductor `c` of ``self`` is inert in K and coprime to `ND`. Moreover, if `n` is not ``None``, also check that for each prime `p` dividing `c` we have that `n | \gcd(a_p(E), p+1)`.
INPUT:
`n` -- positive integer
EXAMPLES::
sage: EllipticCurve('389a').heegner_point(-7).satisfies_kolyvagin_hypothesis() True sage: EllipticCurve('389a').heegner_point(-7,5).satisfies_kolyvagin_hypothesis() True sage: EllipticCurve('389a').heegner_point(-7,11).satisfies_kolyvagin_hypothesis() False """ r=None, n=n, c=self.conductor())
def __hash__(self): """ The hash value is obtained from the elliptic curve and the Heegner point on `X_0(N)`.
EXAMPLES::
sage: x = EllipticCurve('389a').heegner_point(-7,5) sage: hash(x) == hash( (x.curve(), x.heegner_point_on_X0N()) ) True """
def __eq__(self, right): """ EXAMPLES::
sage: y1 = EllipticCurve('389a').heegner_point(-7) sage: y5 = EllipticCurve('389a').heegner_point(-7,5) sage: y1 == y1 True sage: y5 == y5 True sage: y1 == y5 False sage: y1 == 10 False """ (self.__E, self.__x) == (right.__E, right.__x)
def __ne__(self, other): """ EXAMPLES::
sage: y1 = EllipticCurve('389a').heegner_point(-7) sage: y5 = EllipticCurve('389a').heegner_point(-7,5) sage: y1 != y1 False sage: y5 != y5 False sage: y1 != y5 True sage: y1 != 10 True """
def _repr_(self): """ Return string representation of this Heegner point.
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 97) sage: P._repr_() 'Heegner point of discriminant -7 and conductor 97 on elliptic curve of conductor 389' """
def heegner_point_on_X0N(self): r""" Return Heegner point on `X_0(N)` that maps to this Heegner point on `E`.
EXAMPLES::
sage: E = EllipticCurve('37a'); P = E.heegner_point(-7,5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 37 sage: P.heegner_point_on_X0N() Heegner point 5/74*sqrt(-7) - 11/74 of discriminant -7 and conductor 5 on X_0(37) """
def map_to_complex_numbers(self, prec=53): """ Return the point in the subfield `M` of the complex numbers (well defined only modulo the period lattice) corresponding to this Heegner point.
EXAMPLES:
We compute a nonzero Heegner point over a ring class field on a curve of rank 2::
sage: E = EllipticCurve('389a'); y = E.heegner_point(-7,5) sage: y.map_to_complex_numbers() 1.49979679635196 + 0.369156204821526*I sage: y.map_to_complex_numbers(100) 1.4997967963519640592142411892 + 0.36915620482152626830089145962*I sage: y.map_to_complex_numbers(10) 1.5 + 0.37*I
Here we see that the Heegner point is 0 since it lies in the lattice::
sage: E = EllipticCurve('389a'); y = E.heegner_point(-7) sage: y.map_to_complex_numbers(10) 0.0034 - 3.9*I sage: y.map_to_complex_numbers() 4.71844785465692e-15 - 3.94347540310330*I sage: E.period_lattice().basis() (2.49021256085505, 1.97173770155165*I) sage: 2*E.period_lattice().basis()[1] 3.94347540310330*I
You can also directly coerce to the complex field::
sage: E = EllipticCurve('389a'); y = E.heegner_point(-7) sage: z = ComplexField(100)(y); z # real part approx. 0 -... - 3.9434754031032964088448153963*I sage: E.period_lattice().elliptic_exponential(z) (0.00000000000000000000000000000 : 1.0000000000000000000000000000 : 0.00000000000000000000000000000) """
def _complex_mpfr_field_(self, C): """ Used internally for coercing Heegner point to a complex field.
EXAMPLES::
sage: E = EllipticCurve('37a'); y = E.heegner_point(-7) sage: CC(y) # indirect doctest 0.929592715285395 - 1.22569469099340*I sage: ComplexField(100)(y) 0.92959271528539567440519934446 - 1.2256946909933950304271124159*I """
@cached_method def kolyvagin_point(self): """ Return the Kolyvagin point corresponding to this Heegner point.
This is the point obtained by applying the Kolyvagin operator `J_c I_c` in the group ring of the Galois group to this Heegner point. It is a point that defines an element of `H^1(K, E[n])`, under certain hypotheses on `n`.
EXAMPLES::
sage: E = EllipticCurve('37a1'); y = E.heegner_point(-7); y Heegner point of discriminant -7 on elliptic curve of conductor 37 sage: P = y.kolyvagin_point(); P Kolyvagin point of discriminant -7 on elliptic curve of conductor 37 sage: P.numerical_approx() # abs tol 1e-15 (-3.36910401903861e-16 - 2.22076195576076e-16*I : 3.33066907387547e-16 + 2.22076195576075e-16*I : 1.00000000000000) """
@cached_method def _trace_index(self, *args, **kwds): """ Return index of the trace of this Heegner point down to `K` in the group of `K`-rational points.
IMPORTANT: See the help for ``E=self.curve(); E.index?`` for the inputs to this function and more details about what is computed. In particular, the returned index can be off at 2.
OUTPUT:
- ``Integer`` -- returns an integer
EXAMPLES::
sage: E = EllipticCurve('77a1') sage: P = E.heegner_point(-19); y = P._trace_numerical_conductor_1(); [c.real() for c in y] [-1.2...e-16, -1.00000000000000, 1.00000000000000] sage: -2*E.gens()[0] (0 : -1 : 1) sage: P._trace_index() 2
sage: P = E.heegner_point(-68); P Heegner point of discriminant -68 on elliptic curve of conductor 77 sage: N(P) (0.219223593595584 - 1.87443160153148*I : -1.34232921921325 - 1.52356748877889*I : 1.00000000000000) sage: P._trace_index() 0 """ raise ValueError("conductor of Heegner point must be 1") # here we would say raise precision somehow. raise NotImplementedError("unable to compute index")
def curve(self): """ Return the elliptic curve on which this is a Heegner point.
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5) sage: P.curve() Elliptic Curve defined by y^2 + y = x^3 + x^2 - 2*x over Rational Field sage: P.curve() is E True """
@cached_method def quadratic_form(self): """ Return the integral primitive positive definite binary quadratic form associated to this Heegner point.
EXAMPLES::
sage: EllipticCurve('389a').heegner_point(-7, 5).quadratic_form() 389*x^2 + 147*x*y + 14*y^2
sage: P = EllipticCurve('389a').heegner_point(-7, 5, (778,925,275)); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: P.quadratic_form() 778*x^2 + 925*x*y + 275*y^2 """
@cached_method def numerical_approx(self, prec=53, algorithm=None): """ Return a numerical approximation to this Heegner point computed using a working precision of prec bits.
.. WARNING::
The answer is *not* provably correct to prec bits! A priori, due to rounding and other errors, it is possible that not a single digit is correct.
INPUT:
- prec -- (default: ``None``) the working precision
EXAMPLES::
sage: E = EllipticCurve('37a'); P = E.heegner_point(-7); P Heegner point of discriminant -7 on elliptic curve of conductor 37 sage: P.numerical_approx() # abs tol 1e-15 (-3.36910401903861e-16 - 2.22076195576076e-16*I : 3.33066907387547e-16 + 2.22076195576075e-16*I : 1.00000000000000) sage: P.numerical_approx(10) # expect random digits (0.0030 - 0.0028*I : -0.0030 + 0.0028*I : 1.0) sage: P.numerical_approx(100)[0] # expect random digits 8.4...e-31 + 6.0...e-31*I sage: E = EllipticCurve('37a'); P = E.heegner_point(-40); P Heegner point of discriminant -40 on elliptic curve of conductor 37 sage: P.numerical_approx() # abs tol 1e-14 (-3.15940603400359e-16 + 1.41421356237309*I : 1.00000000000000 - 1.41421356237309*I : 1.00000000000000)
A rank 2 curve, where all Heegner points of conductor 1 are 0::
sage: E = EllipticCurve('389a'); E.rank() 2 sage: P = E.heegner_point(-7); P Heegner point of discriminant -7 on elliptic curve of conductor 389 sage: P.numerical_approx() (0.000000000000000 : 1.00000000000000 : 0.000000000000000)
However, Heegner points of bigger conductor are often nonzero::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: numerical_approx(P) (0.675507556926806 + 0.344749649302635*I : -0.377142931401887 + 0.843366227137146*I : 1.00000000000000) sage: P.numerical_approx() (0.6755075569268... + 0.3447496493026...*I : -0.3771429314018... + 0.8433662271371...*I : 1.00000000000000) sage: E.heegner_point(-7, 11).numerical_approx() (0.1795583794118... + 0.02035501750912...*I : -0.5573941377055... + 0.2738940831635...*I : 1.00000000000000) sage: E.heegner_point(-7, 13).numerical_approx() (1.034302915374... - 3.302744319777...*I : 1.323937875767... + 6.908264226850...*I : 1.00000000000000)
We find (probably) the definining polynomial of the `x`-coordinate of `P`, which defines a class field. The shape of the discriminant below is strong confirmation -- but not proof -- that this polynomial is correct::
sage: f = P.numerical_approx(70)[0].algdep(6); f 1225*x^6 + 1750*x^5 - 21675*x^4 - 380*x^3 + 110180*x^2 - 129720*x + 48771 sage: f.discriminant().factor() 2^6 * 3^2 * 5^11 * 7^4 * 13^2 * 19^6 * 199^2 * 719^2 * 26161^2 """
def tau(self): r""" Return `\tau` in the upper half plane that maps via the modular parametrization to this Heegner point.
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5) sage: P.tau() 5/778*sqrt_minus_7 - 147/778 """
@cached_method def x_poly_exact(self, prec=53, algorithm='lll'): """ Return irreducible polynomial over the rational numbers satisfied by the `x` coordinate of this Heegner point. A ValueError is raised if the precision is clearly insignificant to define a point on the curve.
.. WARNING::
It is in theory possible for this function to not raise a ValueError, find a polynomial, but via some very unlikely coincidence that point is not actually this Heegner point.
INPUT:
- ``prec`` -- integer (default: 53)
- ``algorithm`` -- 'conjugates' or 'lll' (default); if 'conjugates', compute numerically all the conjugates ``y[i]`` of the Heegner point and construct the characteristic polynomial as the product `f(X)=(X-y[i])`. If 'lll', compute only one of the conjugates ``y[0]``, then uses the LLL algorithm to guess `f(X)`.
EXAMPLES:
We compute some `x`-coordinate polynomials of some conductor 1 Heegner points::
sage: E = EllipticCurve('37a') sage: v = E.heegner_discriminants_list(10) sage: [E.heegner_point(D).x_poly_exact() for D in v] [x, x, x^2 + 2, x^5 - x^4 + x^3 + x^2 - 2*x + 1, x - 6, x^7 - 2*x^6 + 9*x^5 - 10*x^4 - x^3 + 8*x^2 - 5*x + 1, x^3 + 5*x^2 + 10*x + 4, x^4 - 10*x^3 + 10*x^2 + 12*x - 12, x^8 - 5*x^7 + 7*x^6 + 13*x^5 - 10*x^4 - 4*x^3 + x^2 - 5*x + 7, x^6 - 2*x^5 + 11*x^4 - 24*x^3 + 30*x^2 - 16*x + 4]
We compute `x`-coordinate polynomials for some Heegner points of conductor bigger than 1 on a rank 2 curve::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: P.x_poly_exact() Traceback (most recent call last): ... ValueError: insufficient precision to determine Heegner point (fails discriminant test) sage: P.x_poly_exact(75) x^6 + 10/7*x^5 - 867/49*x^4 - 76/245*x^3 + 3148/35*x^2 - 25944/245*x + 48771/1225 sage: E.heegner_point(-7,11).x_poly_exact(300) x^10 + 282527/52441*x^9 + 27049007420/2750058481*x^8 - 22058564794/2750058481*x^7 - 140054237301/2750058481*x^6 + 696429998952/30250643291*x^5 + 2791387923058/30250643291*x^4 - 3148473886134/30250643291*x^3 + 1359454055022/30250643291*x^2 - 250620385365/30250643291*x + 181599685425/332757076201
Here we compute a Heegner point of conductor 5 on a rank 3 curve::
sage: E = EllipticCurve('5077a'); P = E.heegner_point(-7,5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 5077 sage: P.x_poly_exact(300) x^6 + 1108754853727159228/72351048803252547*x^5 + 88875505551184048168/1953478317687818769*x^4 - 2216200271166098662132/3255797196146364615*x^3 + 14941627504168839449851/9767391588439093845*x^2 - 3456417460183342963918/3255797196146364615*x + 1306572835857500500459/5426328660243941025 """
# If f is correct, then disc(f) = m^2 * (a product of primes dividing D*c). # To check this, we divide out the primes dividing D*c, then # check that the resulting cofactor is a perfect square.
elif algorithm == 'conjugates':
raise NotImplementedError
def _check_poly_discriminant(self, f): """ Return ``True`` if the prime to `Dc` part of the discriminant of each factor of the polynomial `f` is plus or minus a square. This is used for verifying that a polynomial is likely to define a subfield of a specific ring class field.
INPUT:
- `f` -- a polynomial
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: R.<x> = QQ[] sage: P._check_poly_discriminant(x^2 - 5) True sage: P._check_poly_discriminant(x^2 - 19) False sage: P._check_poly_discriminant((x^2 - 19)*(x^2-5)) False """ else: return True
def point_exact(self, prec=53, algorithm='lll', var='a', optimize=False): """ Return exact point on the elliptic curve over a number field defined by computing this Heegner point to the given number of bits of precision. A ValueError is raised if the precision is clearly insignificant to define a point on the curve.
.. WARNING::
It is in theory possible for this function to not raise a ValueError, find a point on the curve, but via some very unlikely coincidence that point is not actually this Heegner point.
.. WARNING::
Currently we make an arbitrary choice of `y`-coordinate for the lift of the `x`-coordinate.
INPUT:
- ``prec`` -- integer (default: 53)
- ``algorithm`` -- see the description of the algorithm parameter for the ``x_poly_exact`` method.
- ``var`` -- string (default: 'a')
- ``optimize`` -- book (default; False) if ``True``, try to optimize defining polynomial for the number field that the point is defined over. Off by default, since this can be very expensive.
EXAMPLES::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-7, 5); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: z = P.point_exact(100, optimize=True) sage: z[1].charpoly() x^12 + 6*x^11 + 90089/1715*x^10 + 71224/343*x^9 + 52563964/588245*x^8 - 483814934/588245*x^7 - 156744579/16807*x^6 - 2041518032/84035*x^5 + 1259355443184/14706125*x^4 + 3094420220918/14706125*x^3 + 123060442043827/367653125*x^2 + 82963044474852/367653125*x + 211679465261391/1838265625 sage: f = P.numerical_approx(500)[1].algdep(12); f / f.leading_coefficient() x^12 + 6*x^11 + 90089/1715*x^10 + 71224/343*x^9 + 52563964/588245*x^8 - 483814934/588245*x^7 - 156744579/16807*x^6 - 2041518032/84035*x^5 + 1259355443184/14706125*x^4 + 3094420220918/14706125*x^3 + 123060442043827/367653125*x^2 + 82963044474852/367653125*x + 211679465261391/1838265625
sage: E = EllipticCurve('5077a') sage: P = E.heegner_point(-7) sage: P.point_exact(prec=100) (0 : 1 : 0) """
# reducible -- 1 factor squared y = F[0][0] L = K # reducible -- 2 factors # y1 = -F[1][0][0] # Figure out which of y0 or y1 is right by # P = self.numerical_approx(prec) # TODO: finish this -- have to do some thing numerical else: # TODO -- is there an issue with choice of root? # irreducible
@cached_method def conjugates_over_K(self): r""" Return the `Gal(K_c/K)` conjugates of this Heegner point.
EXAMPLES::
sage: E = EllipticCurve('77a') sage: y = E.heegner_point(-52,5); y Heegner point of discriminant -52 and conductor 5 on elliptic curve of conductor 77 sage: print([z.quadratic_form() for z in y.conjugates_over_K()]) [77*x^2 + 52*x*y + 13*y^2, 154*x^2 + 206*x*y + 71*y^2, 539*x^2 + 822*x*y + 314*y^2, 847*x^2 + 1284*x*y + 487*y^2, 1001*x^2 + 52*x*y + y^2, 1078*x^2 + 822*x*y + 157*y^2, 1309*x^2 + 360*x*y + 25*y^2, 1309*x^2 + 2054*x*y + 806*y^2, 1463*x^2 + 976*x*y + 163*y^2, 2233*x^2 + 2824*x*y + 893*y^2, 2387*x^2 + 2054*x*y + 442*y^2, 3619*x^2 + 3286*x*y + 746*y^2] sage: y.quadratic_form() 77*x^2 + 52*x*y + 13*y^2 """
def _numerical_approx_conjugates_over_QQ(self, prec=53): """ Return a list v of the numerical approximations to precision prec of the conjugates of this Heegner point, and their complex conjugates.
INPUT:
- ``prec`` -- positive integer (default: 53)
EXAMPLES::
sage: E = EllipticCurve('37a') sage: y = E.heegner_point(-7,3); y Heegner point of discriminant -7 and conductor 3 on elliptic curve of conductor 37 sage: y._numerical_approx_conjugates_over_QQ() [(-1.89564392373896 - 0.444771808762067*I : -1.50000000000000 + 2.13102976222246*I : 1.00000000000000), ...] sage: y._numerical_approx_conjugates_over_QQ(prec=10) [(-1.9 - 0.44*I : -1.5 + 2.1*I : 1.0), ... (1.4 + 0.0024*I : -1.7 - 0.0046*I : 1.0)] """
def _numerical_approx_xy_poly(self, prec=53): r""" Return polynomials with real floating point coefficients got by taking the real part of the product of `X - \alpha` over the numerical approximations `\alpha` to the conjugates of this Heegner point. The first polynomial runs through the `x`-coordinates and the second through the `y`-coordinates.
INPUT:
- ``prec`` -- positive integer (default: 53)
OUTPUT:
- 2-tuple of polynomials with floating point coefficients
EXAMPLES::
sage: E = EllipticCurve('37a') sage: y = E.heegner_point(-7,3); y Heegner point of discriminant -7 and conductor 3 on elliptic curve of conductor 37 sage: y._numerical_approx_xy_poly() # rel tol 1e-14 (X^8 + 6.00000000000000*X^7 + 8.99999999999998*X^6 - 12.0000000000000*X^5 - 42.0000000000000*X^4 - 17.9999999999999*X^3 + 36.0000000000001*X^2 + 35.9999999999999*X + 8.99999999999995, X^8 + 12.0000000000000*X^7 + 72.0000000000000*X^6 + 270.000000000000*X^5 + 678.000000000001*X^4 + 1152.00000000000*X^3 + 1269.00000000000*X^2 + 810.000000000002*X + 225.000000000001) """
def _xy_poly_nearby(self, prec=53, max_error=10**(-10)): """ Return polynomials with rational coefficients that for sufficiently tight bounds are the characteristic polynomial of the x and y coordinate of this Heegner point.
INPUT:
- ``prec`` -- positive integer (default: 53)
- ``max_error`` -- very small floating point number
OUTPUT:
- 2-tuple of polynomials with rational coefficients
EXAMPLES::
sage: E = EllipticCurve('37a') sage: y = E.heegner_point(-7,3); y Heegner point of discriminant -7 and conductor 3 on elliptic curve of conductor 37 sage: y._xy_poly_nearby() [X^8 + 6*X^7 + 9*X^6 - 12*X^5 - 42*X^4 - 18*X^3 + 36*X^2 + 36*X + 9, X^8 + 12*X^7 + 72*X^6 + 270*X^5 + 678*X^4 + 1152*X^3 + 1269*X^2 + 810*X + 225]
"""
def _xy_poly_simplest(self, prec=53, prec2=None): """ Return polynomials with rational coefficients that for sufficiently tight bounds are the characteristic polynomial of the x and y coordinate of this Heegner point.
INPUT:
- ``prec`` -- positive integer (default: 53)
- ``prec2`` -- passed into simplest_rational_poly function
EXAMPLES::
sage: E = EllipticCurve('37a'); y = E.heegner_point(-7,3) sage: y._xy_poly_simplest() [X^8 + 6*X^7 + 9*X^6 - 12*X^5 - 42*X^4 - 18*X^3 + 36*X^2 + 36*X + 9, X^8 + 12*X^7 + 72*X^6 + 270*X^5 + 678*X^4 + 1152*X^3 + 1269*X^2 + 810*X + 225] """
@cached_method def _square_roots_mod_2N_of_D_mod_4N(self): """ Return the square roots of `D` modulo `4N` all reduced mod `2N`, without multiplicity.
EXAMPLES::
sage: E = EllipticCurve('37a'); P = E.heegner_point(-40); P Heegner point of discriminant -40 on elliptic curve of conductor 37 sage: P._square_roots_mod_2N_of_D_mod_4N() [16, 58] sage: parent(P._square_roots_mod_2N_of_D_mod_4N()[0]) Ring of integers modulo 74 """
def _trace_numerical_conductor_1(self, prec=53): """ Return numerical approximation using ``prec`` terms of working precision to the trace down to the quadratic imaginary field `K` of this Heegner point.
INPUT:
- `prec` -- bits precision (default: 53)
EXAMPLES::
sage: E = EllipticCurve('57a1') sage: P = E.heegner_point(-8); P Heegner point of discriminant -8 on elliptic curve of conductor 57 sage: P._trace_numerical_conductor_1() # approx. (1 : 0 : 1) (1.00000000000000 + ...e-16*I : ...e-16 - ...e-16*I : 1.00000000000000) sage: P = E(2,1) # a generator sage: E([1,0]).height() 0.150298370947295 sage: P.height() 0.0375745927368238 sage: E.heegner_index(-8) 2.0000? sage: E.torsion_order() 1 sage: 2*P (1 : 0 : 1) """ raise ValueError("conductor must be 1") s -= t else: else: s -= z else:
@cached_method def _good_tau_representatives(self): """ Return good upper half plane representatives for Heegner points.
ALGORITHM: This is Algorithm 3.5 in Watkins's paper.
EXAMPLES::
sage: P = EllipticCurve('389a1').heegner_point(-7) sage: P._good_tau_representatives() ([(1, 1, 2)], [((389, 185, 22), 1)]) """ # todo (optimize) -- replace for over all s with for over solution # set that can be found quickly. continue # weight is epsilon_Q else: # weight is 2*epsilon_Q assert len(R) < h, "bug -- too many quadratic forms" a += 1
def _qf_to_tau(self, f): r""" Function used internally that given a quadratic form `f=(A,B,C)`, return `\tau` in the upper half plane with `A\tau^2 + B \tau + C = 0`. Here `A>0` and `\gcd(A,B,C)=1`. Also, `\tau` has discriminant `D=B^2-4AC`. In fact, `\tau = (-B + \sqrt{D})/(2A)`.
INPUT:
- `f` -- binary quadratic form
EXAMPLES::
sage: P = EllipticCurve('57a1').heegner_point(-8) sage: R, U = P._good_tau_representatives() sage: f = U[0][0]; f (57, 26, 3) sage: P._qf_to_tau(f) 1/114*sqrt_minus_8 - 13/57 """
def _qf_from_tau(self, tau): r""" Return quadratic form associated to a given `\tau` in the upper half plane.
INPUT:
- `\tau` -- quadratic element of the upper half plane
EXAMPLES::
sage: P = EllipticCurve('57a1').heegner_point(-8) sage: R, U = P._good_tau_representatives() sage: f = U[0][0]; f (57, 26, 3) sage: tau = P._qf_to_tau(f); tau 1/114*sqrt_minus_8 - 13/57 sage: P._qf_from_tau(tau) (57, 26, 3) """
def _qf_atkin_lehner_act(self, Q, f): r""" Given a positive integer `Q` with `Q | N` and `\gcd(Q, N/Q) = 1`, we compute the quadratic form corresponding to the image of the `tau` corresponding to `f` under the Atkin-Lehner operator `W_Q`.
We do this by letting `u,v` be integers such that `u Q^2 - v N = Q`, and using that `W_Q` sends `\tau` to `( (u Q \tau + v) / (N \tau + Q) ) / Q`.
INPUT:
- `Q` -- integer that divides the level `N`
- `f` -- quadratic form
OUTPUT:
- quadratic form
EXAMPLES::
sage: P = EllipticCurve('57a1').heegner_point(-8) sage: R, U = P._good_tau_representatives() sage: f = U[0][0]; f (57, 26, 3) sage: P._qf_atkin_lehner_act(3, f) (1938, 1204, 187) sage: g = P._qf_atkin_lehner_act(19, f); g (114, -64, 9) sage: h = P._qf_atkin_lehner_act(19, g); h (7353, -4762, 771) sage: BinaryQF(f).reduced_form() == BinaryQF(h).reduced_form() True """
def _qf_reduce(self, f): """ Given a binary quadratic form `f` represented as a 3-tuple (A,B,C), return the reduced binary quadratic form equivalent to `f`, represented in the same way.
EXAMPLES::
sage: P = EllipticCurve('57a1').heegner_point(-8) sage: R, U = P._good_tau_representatives() sage: f = U[0][0]; f (57, 26, 3) sage: P._qf_reduce(f) (1, 0, 2) """
def kolyvagin_cohomology_class(self, n=None): """ Return the Kolyvagin class associated to this Heegner point.
INPUT:
- `n` -- positive integer that divides the gcd of `a_p` and `p+1` for all `p` dividing the conductor. If `n` is ``None``, choose the largest valid `n`.
EXAMPLES::
sage: y = EllipticCurve('389a').heegner_point(-7,5) sage: y.kolyvagin_cohomology_class(3) Kolyvagin cohomology class c(5) in H^1(K,E[3]) """
######################################################################################### # Kolyvagin Points P_c ######################################################################################### class KolyvaginPoint(HeegnerPoint): """ A Kolyvagin point.
EXAMPLES:
We create a few Kolyvagin points::
sage: EllipticCurve('11a1').kolyvagin_point(-7) Kolyvagin point of discriminant -7 on elliptic curve of conductor 11 sage: EllipticCurve('37a1').kolyvagin_point(-7) Kolyvagin point of discriminant -7 on elliptic curve of conductor 37 sage: EllipticCurve('37a1').kolyvagin_point(-67) Kolyvagin point of discriminant -67 on elliptic curve of conductor 37 sage: EllipticCurve('389a1').kolyvagin_point(-7, 5) Kolyvagin point of discriminant -7 and conductor 5 on elliptic curve of conductor 389
One can also associated a Kolyvagin point to a Heegner point::
sage: y = EllipticCurve('37a1').heegner_point(-7); y Heegner point of discriminant -7 on elliptic curve of conductor 37 sage: y.kolyvagin_point() Kolyvagin point of discriminant -7 on elliptic curve of conductor 37
TESTS::
sage: y = EllipticCurve('37a1').heegner_point(-7) sage: type(y) <class 'sage.schemes.elliptic_curves.heegner.HeegnerPointOnEllipticCurve'> sage: loads(dumps(y)) == y True """ def __init__(self, heegner_point): """ Create a Kolyvagin point.
INPUT:
- ``heegner_point`` -- a Heegner point on some elliptic curve
EXAMPLES:
We directly construct a Kolyvagin point from the KolyvaginPoint class::
sage: y = EllipticCurve('37a1').heegner_point(-7) sage: sage.schemes.elliptic_curves.heegner.KolyvaginPoint(y) Kolyvagin point of discriminant -7 on elliptic curve of conductor 37 """ raise ValueError("Heegner point does not satisfy Kolyvagin hypothesis") heegner_point.conductor())
def satisfies_kolyvagin_hypothesis(self, n=None): r""" Return ``True`` if this Kolyvagin point satisfies the Heegner hypothesis for `n`, so that it defines a Galois equivariant element of `E(K_c)/n E(K_c)`.
EXAMPLES::
sage: y = EllipticCurve('389a').heegner_point(-7,5); P = y.kolyvagin_point() sage: P.kolyvagin_cohomology_class(3) Kolyvagin cohomology class c(5) in H^1(K,E[3]) sage: P.satisfies_kolyvagin_hypothesis(3) True sage: P.satisfies_kolyvagin_hypothesis(5) False sage: P.satisfies_kolyvagin_hypothesis(7) False sage: P.satisfies_kolyvagin_hypothesis(11) False """
def curve(self): r""" Return the elliptic curve over `\QQ` on which this Kolyvagin point sits.
EXAMPLES::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67, 3) sage: P.curve() Elliptic Curve defined by y^2 + y = x^3 - x over Rational Field """
def heegner_point(self): """ This Kolyvagin point `P_c` is associated to some Heegner point `y_c` via Kolyvagin's construction. This function returns that point `y_c`.
EXAMPLES::
sage: E = EllipticCurve('37a1') sage: P = E.kolyvagin_point(-67); P Kolyvagin point of discriminant -67 on elliptic curve of conductor 37 sage: y = P.heegner_point(); y Heegner point of discriminant -67 on elliptic curve of conductor 37 sage: y.kolyvagin_point() is P True """
def _repr_(self): """ Return string representation of this Kolyvagin point.
EXAMPLES::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67,7); P._repr_() 'Kolyvagin point of discriminant -67 and conductor 7 on elliptic curve of conductor 37' """
def index(self, *args, **kwds): """ Return index of this Kolyvagin point in the full group of $K_c$ rational points on $E$.
When the conductor is 1, this is computed numerically using the Gross-Zagier formula and explicit point search, and it may be off by $2$. See the documentation for ``E.heegner_index``, where `E` is the curve attached to ``self``.
EXAMPLES::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67); P.index() 6 """ raise NotImplementedError
def numerical_approx(self, prec=53): """ Return a numerical approximation to this Kolyvagin point using prec bits of working precision.
INPUT:
- ``prec`` -- precision in bits (default: 53)
EXAMPLES::
sage: P = EllipticCurve('37a1').kolyvagin_point(-7); P Kolyvagin point of discriminant -7 on elliptic curve of conductor 37 sage: P.numerical_approx() # approx. (0 : 0 : 1) (...e-16 - ...e-16*I : ...e-16 + ...e-16*I : 1.00000000000000) sage: P.numerical_approx(100)[0].abs() < 2.0^-99 True
sage: P = EllipticCurve('389a1').kolyvagin_point(-7, 5); P Kolyvagin point of discriminant -7 and conductor 5 on elliptic curve of conductor 389
Numerical approximation is only implemented for points of conductor 1::
sage: P.numerical_approx() Traceback (most recent call last): ... NotImplementedError """
def point_exact(self, prec=53): """ INPUT:
- ``prec`` -- precision in bits (default: 53)
EXAMPLES:
A rank 1 curve::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67) sage: P.point_exact() (6 : -15 : 1) sage: P.point_exact(40) (6 : -15 : 1) sage: P.point_exact(20) Traceback (most recent call last): ... RuntimeError: insufficient precision to find exact point
A rank 0 curve::
sage: E = EllipticCurve('11a1'); P = E.kolyvagin_point(-7) sage: P.point_exact() (-1/2*sqrt_minus_7 + 1/2 : -2*sqrt_minus_7 - 2 : 1)
A rank 2 curve::
sage: E = EllipticCurve('389a1'); P = E.kolyvagin_point(-7) sage: P.point_exact() (0 : 1 : 0)
""" # the result is a point defined over K in the conductor 1 case, which is easier.
else: # root number +1. We use algdep to recognize the x # coordinate, stick it in the appropriate quadratic # field, then make sure that we got the right # embedding, and if not fix things so we do. raise RuntimeError("insufficient precision to find exact point") X = roots[0] else: raise RuntimeError("insufficient precision to distinguish roots") X = roots[0] else: return Q[0] raise RuntimeError("insufficient precision") raise RuntimeError("insufficient precision to distinguish roots") return Q[0] else:
else: raise NotImplementedError
def plot(self, prec=53, *args, **kwds): r""" Plot a Kolyvagin point `P_1` if it is defined over the rational numbers.
EXAMPLES::
sage: E = EllipticCurve('37a'); P = E.heegner_point(-11).kolyvagin_point() sage: P.plot(prec=30, pointsize=50, rgbcolor='red') + E.plot() Graphics object consisting of 3 graphics primitives """ raise NotImplementedError
# point at infinity return Graphics() else: raise NotImplementedError
@cached_method def trace_to_real_numerical(self, prec=53): """ Return the trace of this Kolyvagin point down to the real numbers, computed numerically using prec bits of working precision.
EXAMPLES::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67) sage: PP = P.numerical_approx() sage: [c.real() for c in PP] [6.00000000000000, -15.0000000000000, 1.00000000000000] sage: all([c.imag().abs() < 1e-14 for c in PP]) True sage: P.trace_to_real_numerical() (1.61355529131986 : -2.18446840788880 : 1.00000000000000) sage: P.trace_to_real_numerical(prec=80) # abs tol 1e-21 (1.6135552913198573127230 : -2.1844684078888023289187 : 1.0000000000000000000000)
""" # Compute numerical approximation of P in E(K). # Trace this numerical approximation down to E(Q) (numerically). else:
@cached_method def _trace_exact_conductor_1(self, prec=53): r""" Return the trace from `K` to `\QQ` of this Kolyvagin point in the case of conductor 1, computed using prec bits of precision, then approximated using some algorithm (e.g., continued fractions). If the precision is not enough to determine a point on the curve, then a RuntimeError is raised. Even if the precision determines a point, there is no guarantee that it is correct.
EXAMPLES:
A Kolyvagin point on a rank 1 curve::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67) sage: P.trace_to_real_numerical() (1.61355529131986 : -2.18446840788880 : 1.00000000000000) sage: P._trace_exact_conductor_1() # the actual point we're reducing (1357/841 : -53277/24389 : 1) sage: (P._trace_exact_conductor_1().height() / E.regulator()).sqrt() 12.0000000000000 """ raise ValueError("the conductor must be 1")
def _recognize_point_over_QQ(self, P, n): """ Used internally when computing an exact point on an elliptic curve.
INPUT:
- `P` -- numerical approximation for a point on `E`
- `n` -- upper bound on divisibility index of `P` in group `E(\QQ)`
EXAMPLES::
sage: E = EllipticCurve('43a'); P = E.heegner_point(-20).kolyvagin_point() sage: PP = P.numerical_approx(); PP (...e-16 : -1.00000000000000 : 1.00000000000000) sage: P._recognize_point_over_QQ(PP, 4) (0 : -1 : 1) """ # Here is where we *should* implement the "method of Cremona # etc" mentioned in Watkins' article... which involves local # heights. # note -- we do not claim to prove anything, so making up a factor of 100 is fine. # the coercion below also checks if point is on elliptic curve
def mod(self, p, prec=53): r""" Return the trace of the reduction `Q` modulo a prime over `p` of this Kolyvagin point as an element of `E(\GF{p})`, where `p` is any prime that is inert in `K` that is coprime to `NDc`.
The point `Q` is only well defined up to an element of `(p+1) E(\GF{p})`, i.e., it gives a well defined element of the abelian group `E(\GF{p}) / (p+1) E(\GF{p})`.
See [SteinToward]_, Proposition 5.4 for a proof of the above well-definedness assertion.
EXAMPLES:
A Kolyvagin point on a rank 1 curve::
sage: E = EllipticCurve('37a1'); P = E.kolyvagin_point(-67) sage: P.mod(2) (1 : 1 : 1) sage: P.mod(3) (1 : 0 : 1) sage: P.mod(5) (2 : 2 : 1) sage: P.mod(7) (6 : 0 : 1) sage: P.trace_to_real_numerical() (1.61355529131986 : -2.18446840788880 : 1.00000000000000) sage: P._trace_exact_conductor_1() # the actual point we're reducing (1357/841 : -53277/24389 : 1) sage: (P._trace_exact_conductor_1().height() / E.regulator()).sqrt() 12.0000000000000
Here the Kolyvagin point is a torsion point (since `E` has rank 1), and we reduce it modulo several primes.::
sage: E = EllipticCurve('11a1'); P = E.kolyvagin_point(-7) sage: P.mod(3,70) # long time (4s on sage.math, 2013) (1 : 2 : 1) sage: P.mod(5,70) (1 : 4 : 1) sage: P.mod(7,70) Traceback (most recent call last): ... ValueError: p must be coprime to conductors and discriminant sage: P.mod(11,70) Traceback (most recent call last): ... ValueError: p must be coprime to conductors and discriminant sage: P.mod(13,70) (3 : 4 : 1)
REFERENCES:
.. [SteinToward] Stein, "Toward a Generalization of the Gross-Zagier Conjecture", Int Math Res Notices (2011), :doi:`10.1093/imrn/rnq075` """ # check preconditions raise ValueError("p must be prime") raise ValueError("p must be inert")
# do actual calculation
else:
raise NotImplementedError
## def congruent_rational_point(self, n, prec=53): ## r""" ## Let `P` be this Kolyvagin point. Determine whether there is a ## point `z` in `E(\QQ)` such that `z - P \in n E(K_c)`, where `K_c` ## is the ring class field over which this Kolyvagin point is defined. ## If `z` exists return `z`. Otherwise return None. ## ## INPUT: ## ## - `n` -- positive integer ## ## - ``prec`` -- positive integer (default: 53) ## ## ## EXAMPLES:: ## ## """ ## raise NotImplementedError
def kolyvagin_cohomology_class(self, n=None): """ INPUT:
- `n` -- positive integer that divides the gcd of `a_p` and `p+1` for all `p` dividing the conductor. If `n` is ``None``, choose the largest valid `n`.
EXAMPLES::
sage: y = EllipticCurve('389a').heegner_point(-7,5) sage: P = y.kolyvagin_point() sage: P.kolyvagin_cohomology_class(3) Kolyvagin cohomology class c(5) in H^1(K,E[3])
sage: y = EllipticCurve('37a').heegner_point(-7,5).kolyvagin_point() sage: y.kolyvagin_cohomology_class() Kolyvagin cohomology class c(5) in H^1(K,E[2]) """
class KolyvaginCohomologyClass(SageObject): """ A Kolyvagin cohomology class in `H^1(K,E[n])` or `H^1(K,E)[n]` attached to a Heegner point.
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7) sage: c = y.kolyvagin_cohomology_class(3); c Kolyvagin cohomology class c(1) in H^1(K,E[3]) sage: type(c) <class 'sage.schemes.elliptic_curves.heegner.KolyvaginCohomologyClassEn'> sage: loads(dumps(c)) == c True sage: y.kolyvagin_cohomology_class(5) Kolyvagin cohomology class c(1) in H^1(K,E[5]) """ def __init__(self, kolyvagin_point, n): """
EXAMPLES::
sage: y = EllipticCurve('389a').heegner_point(-7,5) sage: y.kolyvagin_cohomology_class(3) Kolyvagin cohomology class c(5) in H^1(K,E[3]) """
raise ValueError("Kolyvagin point does not satisfy Kolyvagin hypothesis for %s"%n)
def __eq__(self, other): """ EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7) sage: c = y.kolyvagin_cohomology_class(3) sage: c == y.kolyvagin_cohomology_class(3) True sage: c == y.kolyvagin_cohomology_class(5) False
This does not mean that c is nonzero (!) -- it just means c is not the number 0::
sage: c == 0 False """ self.__kolyvagin_point == other.__kolyvagin_point and \ self.__n == other.__n
def __ne__(self, other): """ EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7) sage: c = y.kolyvagin_cohomology_class(3) sage: c != y.kolyvagin_cohomology_class(3) False sage: c != y.kolyvagin_cohomology_class(5) True """
def n(self): """ Return the integer `n` so that this is a cohomology class in `H^1(K,E[n])` or `H^1(K,E)[n]`.
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7) sage: t = y.kolyvagin_cohomology_class(3); t Kolyvagin cohomology class c(1) in H^1(K,E[3]) sage: t.n() 3 """
def conductor(self): r""" Return the integer `c` such that this cohomology class is associated to the Heegner point `y_c`.
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7,5) sage: t = y.kolyvagin_cohomology_class() sage: t.conductor() 5 """
def kolyvagin_point(self): """ Return the Kolyvagin point `P_c` to which this cohomology class is associated.
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7,5) sage: t = y.kolyvagin_cohomology_class() sage: t.kolyvagin_point() Kolyvagin point of discriminant -7 and conductor 5 on elliptic curve of conductor 37 """
def heegner_point(self): """ Return the Heegner point `y_c` to which this cohomology class is associated.
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7,5) sage: t = y.kolyvagin_cohomology_class() sage: t.heegner_point() Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 37 """
class KolyvaginCohomologyClassEn(KolyvaginCohomologyClass): """
EXAMPLES:
""" def _repr_(self): """
EXAMPLES::
sage: y = EllipticCurve('37a').heegner_point(-7,5) sage: t = y.kolyvagin_cohomology_class() sage: t._repr_() 'Kolyvagin cohomology class c(5) in H^1(K,E[2])' """ self.conductor(), self.n())
############################################################################# # Reduction of Heegner points using Quaternion Algebras # # This section contains implementations of algorithms for computing # information about reduction modulo primes of Heegner points using # quaternion algebras. Some of this code could later be moved to the # quaternion algebras code, but it is too immature and not general # enough at present for that. #############################################################################
class HeegnerQuatAlg(SageObject): r""" Heegner points viewed as supersingular points on the modular curve `X_0(N)/\mathbf{F}_{\ell}`.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(13); H Heegner points on X_0(11) over F_13 sage: type(H) <class 'sage.schemes.elliptic_curves.heegner.HeegnerQuatAlg'> sage: loads(dumps(H)) == H True """ def __init__(self, level, ell): r""" INPUT:
- ``level`` -- the level (a positive integer)
- `\ell` -- the characteristic, a prime coprime to the level
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.HeegnerQuatAlg(11, 13) Heegner points on X_0(11) over F_13 """ raise ValueError("ell must be prime") raise ValueError("level and ell must be coprime")
def __eq__(self, other): """ EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3) sage: H == heegner_points(11).reduce_mod(3) True sage: H == heegner_points(11).reduce_mod(5) False sage: H == 0 False """ and self.__ell == other.__ell
def __ne__(self, other): """ EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3) sage: H != heegner_points(11).reduce_mod(3) False sage: H != heegner_points(11).reduce_mod(5) True sage: H != 0 True """
def _repr_(self): """ Return string representation.
EXAMPLES::
sage: heegner_points(11).reduce_mod(13)._repr_() 'Heegner points on X_0(11) over F_13' """ self.__level, self.__ell)
def level(self): """ Return the level.
EXAMPLES::
sage: heegner_points(11).reduce_mod(3).level() 11 """
def ell(self): r""" Return the prime `\ell` modulo which we are working.
EXAMPLES::
sage: heegner_points(11).reduce_mod(3).ell() 3 """
def satisfies_heegner_hypothesis(self, D, c=ZZ(1)): r""" The fundamental discriminant `D` must be coprime to `N\ell`, and must define a quadratic imaginary field `K` in which `\ell` is inert. Also, all primes dividing `N` must split in `K`, and `c` must be squarefree and coprime to `ND\ell`.
INPUT:
- `D` -- negative integer
- `c` -- positive integer (default: 1)
OUTPUT:
- bool
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(7) sage: H.satisfies_heegner_hypothesis(-5) False sage: H.satisfies_heegner_hypothesis(-7) False sage: H.satisfies_heegner_hypothesis(-8) True sage: [D for D in [-1,-2..-100] if H.satisfies_heegner_hypothesis(D)] [-8, -39, -43, -51, -79, -95] """
def heegner_discriminants(self, n=5): r""" Return the first `n` negative fundamental discriminants coprime to `N\ell` such that `\ell` is inert in the corresponding quadratic imaginary field and that field satisfies the Heegner hypothesis, and `N` is the level.
INPUT:
- `n` -- positive integer (default: 5)
OUTPUT:
- list
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3) sage: H.heegner_discriminants() [-7, -19, -40, -43, -52] sage: H.heegner_discriminants(10) [-7, -19, -40, -43, -52, -79, -127, -139, -151, -184] """
def heegner_conductors(self, D, n=5): r""" Return the first `n` negative fundamental discriminants coprime to `N\ell` such that `\ell` is inert in the corresponding quadratic imaginary field and that field satisfies the Heegner hypothesis.
INPUT:
- `D` -- negative integer; a fundamental Heegner discriminant
- `n` -- positive integer (default: 5)
OUTPUT:
- list
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3) sage: H.heegner_conductors(-7) [1, 2, 4, 5, 8] sage: H.heegner_conductors(-7, 10) [1, 2, 4, 5, 8, 10, 13, 16, 17, 19] """
def optimal_embeddings(self, D, c, R): """ INPUT:
- `D` -- negative fundamental discriminant
- `c` -- integer coprime
- `R` -- Eichler order
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3) sage: R = H.left_orders()[0] sage: H.optimal_embeddings(-7, 1, R) [Embedding sending sqrt(-7) to i - j - k, Embedding sending sqrt(-7) to -i + j + k] sage: H.optimal_embeddings(-7, 2, R) [Embedding sending 2*sqrt(-7) to 5*i - k, Embedding sending 2*sqrt(-7) to -5*i + k, Embedding sending 2*sqrt(-7) to 2*i - 2*j - 2*k, Embedding sending 2*sqrt(-7) to -2*i + 2*j + 2*k] """
# The representatives give elements in terms of the # subspace's basis such that the embedding is given by # phi(c*sqrt(D)) = beta
@cached_method def brandt_module(self): """ Return the Brandt module of right ideal classes that we used to represent the set of supersingular points on the modular curve.
EXAMPLES::
sage: heegner_points(11).reduce_mod(3).brandt_module() Brandt module of dimension 2 of level 3*11 of weight 2 over Rational Field """
@cached_method def quaternion_algebra(self): """ Return the rational quaternion algebra used to implement self.
EXAMPLES::
sage: heegner_points(389).reduce_mod(7).quaternion_algebra() Quaternion Algebra (-1, -7) with base ring Rational Field """
def right_ideals(self): """ Return representative right ideals in the Brandt module.
EXAMPLES::
sage: heegner_points(11).reduce_mod(3).right_ideals() (Fractional ideal (2 + 2*j + 28*k, 2*i + 26*k, 4*j + 12*k, 44*k), Fractional ideal (2 + 2*j + 28*k, 2*i + 4*j + 38*k, 8*j + 24*k, 88*k)) """
@cached_method def left_orders(self): """ Return the left orders associated to the representative right ideals in the Brandt module.
EXAMPLES::
sage: heegner_points(11).reduce_mod(3).left_orders() [Order of Quaternion Algebra (-1, -3) with base ring Rational Field with basis (1/2 + 1/2*j + 7*k, 1/2*i + 13/2*k, j + 3*k, 11*k), Order of Quaternion Algebra (-1, -3) with base ring Rational Field with basis (1/2 + 1/2*j + 7*k, 1/4*i + 1/2*j + 63/4*k, j + 14*k, 22*k)] """
@cached_method def heegner_divisor(self, D, c=ZZ(1)): r""" Return Heegner divisor as an element of the Brandt module corresponding to the discriminant `D` and conductor `c`, which both must be coprime to `N\ell`.
More precisely, we compute the sum of the reductions of the `\textrm{Gal}(K_1/K)`-conjugates of each choice of `y_1`, where the choice comes from choosing the ideal `\mathcal{N}`. Then we apply the Hecke operator `T_c` to this sum.
INPUT:
- `D` -- discriminant (negative integer)
- `c` -- conductor (positive integer)
OUTPUT:
- Brandt module element
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(7) sage: H.heegner_discriminants() [-8, -39, -43, -51, -79] sage: H.heegner_divisor(-8) (1, 0, 0, 1, 0, 0) sage: H.heegner_divisor(-39) (1, 2, 2, 1, 2, 0) sage: H.heegner_divisor(-43) (1, 0, 0, 1, 0, 0) sage: H.heegner_divisor(-51) (1, 0, 0, 1, 0, 2) sage: H.heegner_divisor(-79) (3, 2, 2, 3, 0, 0)
sage: sum(H.heegner_divisor(-39).element()) 8 sage: QuadraticField(-39,'a').class_number() 4 """ raise ValueError("D and c must be coprime to N and ell")
# Just apply T_c to divisor for c=1 z = self.heegner_divisor(D) return B.hecke_operator(c)(z)
@cached_method def modp_splitting_data(self, p): r""" Return mod `p` splitting data for the quaternion algebra at the unramified prime `p`. This is a pair of `2\times 2` matrices `A`, `B` over the finite field `\GF{p}` such that if the quaternion algebra has generators `i, j, k`, then the homomorphism sending `i` to `A` and `j` to `B` maps any maximal order homomorphically onto the ring of `2\times 2` matrices.
Because of how the homomorphism is defined, we must assume that the prime `p` is odd.
INPUT:
- `p` -- unramified odd prime
OUTPUT:
- 2-tuple of matrices over finite field
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(7) sage: H.quaternion_algebra() Quaternion Algebra (-1, -7) with base ring Rational Field sage: I, J = H.modp_splitting_data(13) sage: I [ 0 12] [ 1 0] sage: J [7 3] [3 6] sage: I^2 [12 0] [ 0 12] sage: J^2 [6 0] [0 6] sage: I*J == -J*I True
The following is a good test because of the asserts in the code::
sage: v = [H.modp_splitting_data(p) for p in primes(13,200)]
Some edge cases::
sage: H.modp_splitting_data(11) ( [ 0 10] [6 1] [ 1 0], [1 5] )
Proper error handling::
sage: H.modp_splitting_data(7) Traceback (most recent call last): ... ValueError: p (=7) must be an unramified prime
sage: H.modp_splitting_data(2) Traceback (most recent call last): ... ValueError: p must be odd """ raise ValueError("p (=%s) must be prime"%p) #for b in reversed(list(F)):
def modp_splitting_map(self, p): r""" Return (algebra) map from the (`p`-integral) quaternion algebra to the set of `2\times 2` matrices over `\GF{p}`.
INPUT:
- `p` -- prime number
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(7) sage: f = H.modp_splitting_map(13) sage: B = H.quaternion_algebra(); B Quaternion Algebra (-1, -7) with base ring Rational Field sage: i,j,k = H.quaternion_algebra().gens() sage: a = 2+i-j+3*k; b = 7+2*i-4*j+k sage: f(a*b) [12 3] [10 5] sage: f(a)*f(b) [12 3] [10 5] """
def cyclic_subideal_p1(self, I, c): r""" Compute dictionary mapping 2-tuples that defined normalized elements of `P^1(\ZZ/c\ZZ)`
INPUT:
- `I` -- right ideal of Eichler order or in quaternion algebra
- `c` -- square free integer (currently must be odd prime and coprime to level, discriminant, characteristic, etc.
OUTPUT:
- dictionary mapping 2-tuples (u,v) to ideals
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(7) sage: I = H.brandt_module().right_ideals()[0] sage: sorted(H.cyclic_subideal_p1(I,3).items()) [((0, 1), Fractional ideal (2 + 2*j + 32*k, 2*i + 8*j + 82*k, 12*j + 60*k, 132*k)), ((1, 0), Fractional ideal (2 + 10*j + 28*k, 2*i + 4*j + 62*k, 12*j + 60*k, 132*k)), ((1, 1), Fractional ideal (2 + 2*j + 76*k, 2*i + 4*j + 106*k, 12*j + 60*k, 132*k)), ((1, 2), Fractional ideal (2 + 10*j + 116*k, 2*i + 8*j + 38*k, 12*j + 60*k, 132*k))] sage: len(H.cyclic_subideal_p1(I,17)) 18 """ raise NotImplementedError("currently c must be prime") raise NotImplementedError("currently c must be odd") # Actually they are submodules despite the name below.
@cached_method def galois_group_over_hilbert_class_field(self, D, c): """ Return the Galois group of the extension of ring class fields `K_c` over the Hilbert class field `K_{1}` of the quadratic imaginary field of discriminant `D`.
INPUT:
- `D` -- fundamental discriminant
- `c` -- conductor (square-free integer)
EXAMPLES::
sage: N = 37; D = -7; ell = 17; c = 41; p = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: H.galois_group_over_hilbert_class_field(D, c) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 41 over Hilbert class field of QQ[sqrt(-7)] """
@cached_method def galois_group_over_quadratic_field(self, D, c): """ Return the Galois group of the extension of ring class fields `K_c` over the quadratic imaginary field `K` of discriminant `D`.
INPUT:
- `D` -- fundamental discriminant
- `c` -- conductor (square-free integer)
EXAMPLES::
sage: N = 37; D = -7; ell = 17; c = 41; p = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: H.galois_group_over_quadratic_field(D, c) Galois group of Ring class field extension of QQ[sqrt(-7)] of conductor 41 over Number Field in sqrt_minus_7 with defining polynomial x^2 + 7
"""
@cached_method def quadratic_field(self, D): """ Return our fixed choice of quadratic imaginary field of discriminant `D`.
INPUT:
- `D` -- fundamental discriminant
OUTPUT:
- a quadratic number field
EXAMPLES::
sage: H = heegner_points(389).reduce_mod(5) sage: H.quadratic_field(-7) Number Field in sqrt_minus_7 with defining polynomial x^2 + 7 """
@cached_method def kolyvagin_cyclic_subideals(self, I, p, alpha_quaternion): r""" Return list of pairs `(J, n)` where `J` runs through the cyclic subideals of `I` of index `(\ZZ/p\ZZ)^2`, and `J \sim \alpha^n(J_0)` for some fixed choice of cyclic subideal `J_0`.
INPUT:
- `I` -- right ideal of the quaternion algebra
- `p` -- prime number
- ``alpha_quaternion`` -- image in the quaternion algebra of generator `\alpha` for `(\mathcal{O}_K / c\mathcal{O}_K)^* / (\ZZ/c\ZZ)^*`.
OUTPUT:
- list of 2-tuples
EXAMPLES::
sage: N = 37; D = -7; ell = 17; c=5 sage: H = heegner_points(N).reduce_mod(ell) sage: B = H.brandt_module(); I = B.right_ideals()[32] sage: f = H.optimal_embeddings(D, 1, I.left_order())[1] sage: g = H.kolyvagin_generators(f.domain().number_field(), c) sage: alpha_quaternion = f(g[0]); alpha_quaternion 1 - 5/128*i - 77/192*j + 137/384*k sage: H.kolyvagin_cyclic_subideals(I, 5, alpha_quaternion) [(Fractional ideal (2 + 874/3*j + 128356/3*k, 2*i + 932/3*j + 198806/3*k, 2560/3*j + 33280/3*k, 94720*k), 0), (Fractional ideal (2 + 462*j + 82892*k, 2*i + 932/3*j + 141974/3*k, 2560/3*j + 33280/3*k, 94720*k), 1), (Fractional ideal (2 + 2410/3*j + 261988/3*k, 2*i + 652*j + 89650*k, 2560/3*j + 33280/3*k, 94720*k), 2), (Fractional ideal (2 + 2410/3*j + 91492/3*k, 2*i + 1444/3*j + 148630/3*k, 2560/3*j + 33280/3*k, 94720*k), 3), (Fractional ideal (2 + 874/3*j + 71524/3*k, 2*i + 2468/3*j + 275606/3*k, 2560/3*j + 33280/3*k, 94720*k), 4), (Fractional ideal (2 + 462*j + 63948*k, 2*i + 2468/3*j + 218774/3*k, 2560/3*j + 33280/3*k, 94720*k), 5)] """
@cached_method def kolyvagin_generator(self, K, p): r""" Return element in `K` that maps to the multiplicative generator for the quotient group
`(\mathcal{O}_K / p \mathcal{O}_K)^* / (\ZZ/p\ZZ)^*`
of the form `\sqrt{D}+n` with `n\geq 1` minimal.
INPUT:
- `K` -- quadratic imaginary field
- `p` -- inert prime
EXAMPLES::
sage: N = 37; D = -7; ell = 17; p=5 sage: H = heegner_points(N).reduce_mod(ell) sage: B = H.brandt_module(); I = B.right_ideals()[32] sage: f = H.optimal_embeddings(D, 1, I.left_order())[0] sage: H.kolyvagin_generator(f.domain().number_field(), 5) a + 1
This function requires that p be prime, but kolyvagin_generators works in general::
sage: H.kolyvagin_generator(f.domain().number_field(), 5*17) Traceback (most recent call last): ... NotImplementedError: p must be prime sage: H.kolyvagin_generators(f.domain().number_field(), 5*17) [-34*a + 1, 35*a + 106] """ raise ValueError("p must be unramified") raise ValueError("p must be inert")
raise RuntimeError("there is a bug in kolyvagin_generator")
@cached_method def kolyvagin_generators(self, K, c): r""" Return elements in `\mathcal{O}_K` that map to multiplicative generators for the factors of the quotient group
`(\mathcal{O}_K / c \mathcal{O}_K)^* / (\ZZ/c\ZZ)^*`
corresponding to the prime divisors of c. Each generator is of the form `\sqrt{D}+n` with `n\geq 1` minimal.
INPUT:
- `K` -- quadratic imaginary field
- `c` -- square free product of inert prime
EXAMPLES::
sage: N = 37; D = -7; ell = 17; p=5 sage: H = heegner_points(N).reduce_mod(ell) sage: B = H.brandt_module(); I = B.right_ideals()[32] sage: f = H.optimal_embeddings(D, 1, I.left_order())[0] sage: H.kolyvagin_generators(f.domain().number_field(), 5*17) [-34*a + 1, 35*a + 106] """ raise ValueError("c must be square free") # Now we use the Chinese Remainder Theorem to make an element # of O_K that equals alpha modulo p and equals 1 modulo # all other prime divisors of c.
@cached_method def kolyvagin_sigma_operator(self, D, c, r, bound=None): """ Return the action of the Kolyvagin sigma operator on the `r`-th basis vector.
INPUT:
- `D` -- fundamental discriminant
- `c` -- conductor (square-free integer, need not be prime)
- `r` -- nonnegative integer
- ``bound`` -- (default: ``None``), if given, controls precision of computation of theta series, which could impact performance, but does not impact correctness
EXAMPLES:
We first try to verify Kolyvagin's conjecture for a rank 2 curve by working modulo 5, but we are unlucky with `c=17`::
sage: N = 389; D = -7; ell = 5; c = 17; q = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: E = EllipticCurve('389a') sage: V = H.modp_dual_elliptic_curve_factor(E, q, 5) # long time (4s on sage.math, 2012) sage: k118 = H.kolyvagin_sigma_operator(D, c, 118) sage: k104 = H.kolyvagin_sigma_operator(D, c, 104) sage: [b.dot_product(k104.element().change_ring(GF(3))) for b in V.basis()] # long time [0, 0] sage: [b.dot_product(k118.element().change_ring(GF(3))) for b in V.basis()] # long time [0, 0]
Next we try again with `c=41` and this does work, in that we get something nonzero, when dotting with V::
sage: c = 41 sage: k118 = H.kolyvagin_sigma_operator(D, c, 118) sage: k104 = H.kolyvagin_sigma_operator(D, c, 104) sage: [b.dot_product(k118.element().change_ring(GF(3))) for b in V.basis()] # long time [2, 0] sage: [b.dot_product(k104.element().change_ring(GF(3))) for b in V.basis()] # long time [1, 0]
By the way, the above is the first ever provable verification of Kolyvagin's conjecture for any curve of rank at least 2.
Another example, but where the curve has rank 1::
sage: N = 37; D = -7; ell = 17; c = 41; q = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: H.heegner_divisor(D,1).element().nonzero_positions() [32, 51] sage: k32 = H.kolyvagin_sigma_operator(D, c, 32); k32 (17, 12, 33, 33, 49, 108, 3, 0, 0, 33, 37, 49, 33, 33, 59, 54, 21, 30, 0, 0, 29, 12, 41, 38, 33, 15, 0, 0, 4, 0, 7, 0, 0, 0, 0, 34, 26, 18, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) sage: k51 = H.kolyvagin_sigma_operator(D, c, 51); k51 (5, 13, 0, 0, 14, 0, 21, 0, 0, 0, 29, 0, 0, 45, 0, 6, 0, 40, 0, 61, 0, 0, 40, 32, 0, 9, 0, 0, 0, 0, 17, 0, 0, 0, 77, 40, 2, 10, 18, 0, 0, 61, 19, 45, 26, 80, 61, 35, 35, 19, 1, 0) sage: V = H.modp_dual_elliptic_curve_factor(EllipticCurve('37a'), q, 5); V Vector space of degree 52 and dimension 2 over Ring of integers modulo 3 Basis matrix: 2 x 52 dense matrix over Ring of integers modulo 3 sage: [b.dot_product(k32.element().change_ring(GF(q))) for b in V.basis()] [2, 2] sage: [b.dot_product(k51.element().change_ring(GF(q))) for b in V.basis()] [1, 1]
An example with `c` a product of two primes::
sage: N = 389; D = -7; ell = 5; q = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: V = H.modp_dual_elliptic_curve_factor(EllipticCurve('389a'), q, 5) sage: k = H.kolyvagin_sigma_operator(D, 17*41, 104) # long time sage: k # long time (990, 656, 219, ..., 246, 534, 1254) sage: [b.dot_product(k.element().change_ring(GF(3))) for b in V.basis()] # long time (but only because depends on something slow) [0, 0] """
J = J.intersection(J_lists[i][v[i]]) else: for z in d: if RI[z].is_equivalent(J, 0): j = z # we found the right j break raise RuntimeError("bug finding equivalent ideal")
@cached_method def modp_dual_elliptic_curve_factor(self, E, p, bound=10): """ Return the factor of the Brandt module space modulo `p` corresponding to the elliptic curve `E`, cut out using Hecke operators up to ``bound``.
INPUT:
- `E` -- elliptic curve of conductor equal to the level of self
- `p` -- prime number
- `bound` -- positive integer (default: 10)
EXAMPLES::
sage: N = 37; D = -7; ell = 17; c = 41; q = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: V = H.modp_dual_elliptic_curve_factor(EllipticCurve('37a'), q, 5); V Vector space of degree 52 and dimension 2 over Ring of integers modulo 3 Basis matrix: 2 x 52 dense matrix over Ring of integers modulo 3 """ raise ValueError("conductor of E must equal level of self") raise ValueError("p (=%s) must be prime"%p)
else: t = T.restrict(V) W = (t - E.ap(q)).kernel() V = (W.basis_matrix() * V.basis_matrix()).row_space()
@cached_method def rational_kolyvagin_divisor(self, D, c): r""" Return the Kolyvagin divisor as an element of the Brandt module corresponding to the discriminant `D` and conductor `c`, which both must be coprime to `N\ell`.
INPUT:
- `D` -- discriminant (negative integer)
- `c` -- conductor (positive integer)
OUTPUT:
- Brandt module element (or tuple of them)
EXAMPLES::
sage: N = 389; D = -7; ell = 5; c = 17; q = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: k = H.rational_kolyvagin_divisor(D, c); k # long time (5s on sage.math, 2013) (2, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 4, 0, 0, 9, 11, 0, 6, 0, 0, 7, 0, 0, 0, 0, 14, 12, 13, 15, 17, 0, 0, 0, 0, 8, 0, 0, 0, 0, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) sage: V = H.modp_dual_elliptic_curve_factor(EllipticCurve('389a'), q, 2) sage: [b.dot_product(k.element().change_ring(GF(q))) for b in V.basis()] # long time [0, 0] sage: k = H.rational_kolyvagin_divisor(D, 59) sage: [b.dot_product(k.element().change_ring(GF(q))) for b in V.basis()] [2, 0] """ raise ValueError("D and c must be coprime to N and ell")
raise NotImplementedError("class number greater than 1 not implemented")
#w = 0 #for i, a in six.iteritems(v.dict()): # w += a * self.kolyvagin_sigma_operator(D, c, i) # return w
@cached_method def kolyvagin_point_on_curve(self, D, c, E, p, bound=10): r""" Compute image of the Kolyvagin divisor `P_c` in `E(\GF{\ell^2}) / p E(\GF{\ell^2})`.
Note that this image is by definition only well defined up to scalars. However, doing multiple computations will always yield the same result, and working modulo different `\ell` is compatible (since we always choose the same generator for `\textrm{Gal}(K_c/K_1)`).
INPUT:
- `D` -- fundamental negative discriminant
- `c` -- conductor
- `E` -- elliptic curve of conductor the level of self
- `p` -- odd prime number such that we consider image in `E(\GF{\ell^2}) / p E(\GF{\ell^2})`
- ``bound`` -- integer (default: 10)
EXAMPLES::
sage: N = 37; D = -7; ell = 17; c = 41; p = 3 sage: H = heegner_points(N).reduce_mod(ell) sage: H.kolyvagin_point_on_curve(D, c, EllipticCurve('37a'), p) [2, 2] """
def kolyvagin_reduction_data(E, q, first_only=True): r""" Given an elliptic curve of positive rank and a prime `q`, this function returns data about how to use Kolyvagin's `q`-torsion Heegner point Euler system to do computations with this curve. See the precise description of the output below.
INPUT:
- `E` -- elliptic curve over `\QQ` of rank 1 or 2
- `q` -- an odd prime that does not divide the order of the rational torsion subgroup of `E`
- ``first_only`` -- bool (default: ``True``) whether two only return the first prime that one can work modulo to get data about the Euler system
OUTPUT in the rank 1 case or when the default flag ``first_only=True``:
- `\ell` -- first good odd prime satisfying the Kolyvagin condition that `q` divides \gcd(a_{\ell},\ell+1)` and the reduction map is surjective to `E(\GF{\ell}) / q E(\GF{\ell})`
- `D` -- discriminant of the first quadratic imaginary field `K` that satisfies the Heegner hypothesis for `E` such that both `\ell` is inert in `K`, and the twist `E^D` has analytic rank `\leq 1`
- `h_D` -- the class number of `K`
- the dimension of the Brandt module `B(\ell,N)`, where `N` is the conductor of `E`
OUTPUT in the rank 2 case:
- `\ell_1` -- first prime (as above in the rank 1 case) where reduction map is surjective
- `\ell_2` -- second prime (as above) where reduction map is surjective
- `D` -- discriminant of the first quadratic imaginary field `K` that satisfies the Heegner hypothesis for `E` such that both `\ell_1` and `\ell_2` are simultaneously inert in `K`, and the twist `E^D` has analytic rank `\leq 1`
- `h_D` -- the class number of `K`
- the dimension of the Brandt module `B(\ell_1,N)`, where `N` is the conductor of `E`
- the dimension of the Brandt module `B(\ell_2,N)`
EXAMPLES:
Import this function::
sage: from sage.schemes.elliptic_curves.heegner import kolyvagin_reduction_data
A rank 1 example::
sage: kolyvagin_reduction_data(EllipticCurve('37a1'),3) (17, -7, 1, 52)
A rank 3 example::
sage: kolyvagin_reduction_data(EllipticCurve('5077a1'),3) (11, -47, 5, 4234) sage: H = heegner_points(5077, -47) sage: [c for c in H.kolyvagin_conductors(2,10,EllipticCurve('5077a1'),3) if c%11] [667, 943, 1189, 2461] sage: factor(667) 23 * 29
A rank 4 example (the first Kolyvagin class that we could try to compute would be `P_{23\cdot 29\cdot 41}`, and would require working in a space of dimension 293060 (so prohibitive at present)::
sage: E = elliptic_curves.rank(4)[0] sage: kolyvagin_reduction_data(E,3) # long time (11, -71, 7, 293060) sage: H = heegner_points(293060, -71) sage: H.kolyvagin_conductors(1,4,E,3) [11, 17, 23, 41]
The first rank 2 example::
sage: kolyvagin_reduction_data(EllipticCurve('389a'),3) (5, -7, 1, 130) sage: kolyvagin_reduction_data(EllipticCurve('389a'),3, first_only=False) (5, 17, -7, 1, 130, 520)
A large `q = 7`::
sage: kolyvagin_reduction_data(EllipticCurve('1143c1'),7, first_only=False) (13, 83, -59, 3, 1536, 10496)
Additive reduction::
sage: kolyvagin_reduction_data(EllipticCurve('2350g1'),5, first_only=False) (19, 239, -311, 19, 6480, 85680) """ raise TypeError("E must be an elliptic curve")
raise ValueError("q must be a prime")
raise NotImplementedError("q must be coprime to torsion")
raise ValueError("E must have positive rank")
# return True if the quadratic twist E^D has analytic rank <= 1
# reduce the point P on the elliptic curve modulo ell
# return the first Heegner D satisfy all hypothesis such that # both ell_1 and ell_2 are inert D%ell_1 and D%ell_2 and \ E.satisfies_heegner_hypothesis(D) and \ is_inert(D, ell_1) and is_inert(D, ell_2) and \ twist_is_minimal(D):
# find first prime ell with various conditions # such that reduction is surjective to E(F_ell)/q. # determine if mod ell reduction is surjective, using # partly that it is a lemma that E(F_ell)/q is cyclic. # bingo, is surjective # end for ell = ell.next_prime()
raise ValueError("if first_only is not True, then the curve E must have rank 1 or 2")
# return list of reps for the kernel as a subgroup of the map # E(Q) / q E(Q) ----> E(F_ell) / q E(F_ell)
# compute first good odd prime # compute kernel of reduction modulo ell_1 ell_1 = ell_1.next_prime()
# compute next good odd prime with distinct kernel of order q
# Find smallest D where both ell_1 and ell_2 are inert BrandtModule(ell_1,N).dimension(), BrandtModule(ell_2,N).dimension())
class HeegnerQuatAlgEmbedding(SageObject): r""" The homomorphism `\mathcal{O} \to R`, where `\mathcal{O}` is the order of conductor `c` in the quadratic field of discriminant `D`, and `R` is an Eichler order in a quaternion algebra.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[1]; f Embedding sending 2*sqrt(-7) to -5*i + k sage: type(f) <class 'sage.schemes.elliptic_curves.heegner.HeegnerQuatAlgEmbedding'> sage: loads(dumps(f)) == f True """ def __init__(self, D, c, R, beta): r""" INPUT:
- `D` -- negative fundamental discriminant
- `c` -- positive integer coprime to `D`
- `R` -- Eichler order in a rational quaternion algebra
- `\beta` -- element of `R` such that the homomorphism sends `c\sqrt{D}` to `\beta`
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: i,j,k = H.quaternion_algebra().gens() sage: import sage.schemes.elliptic_curves.heegner as heegner sage: heegner.HeegnerQuatAlgEmbedding(-7, 2, R, -5*i+k) Embedding sending 2*sqrt(-7) to -5*i + k """
def __eq__(self, other): """ EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[0] sage: f == H.optimal_embeddings(-7, 2, R)[0] True sage: f == H.optimal_embeddings(-7, 2, R)[1] False sage: f == 0 False """ self.__D == other.__D and \ self.__c == other.__c and \ self.__R == other.__R and \ self.__beta == other.__beta
def __ne__(self, other): """ EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[0] sage: f != H.optimal_embeddings(-7, 2, R)[0] False sage: f != H.optimal_embeddings(-7, 2, R)[1] True sage: f != 0 True """
def __call__(self, x): """ Return image of `x` under this embedding.
INPUT:
- `x` -- element of the quadratic order
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 1, R)[1]; f Embedding sending sqrt(-7) to -i + j + k sage: a = f.domain_gen(); a^2 -7 sage: f(2 + 3*a) 2 - 3*i + 3*j + 3*k sage: 2 + 3*f(a) 2 - 3*i + 3*j + 3*k sage: f(a)^2 -7 """ # There is no notion of an "element of an order" implemented # for quaternion algebras right now. All elements are # elements of the ambient rational quaternion algebra.
@cached_method def matrix(self): r""" Return matrix over `\QQ` of this morphism, with respect to the basis 1, `c\sqrt{D}` of the domain and the basis `1,i,j,k` of the ambient rational quaternion algebra (which contains the domain).
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 1, R)[1]; f Embedding sending sqrt(-7) to -i + j + k sage: f.matrix() [ 1 0 0 0] [ 0 -1 1 1] sage: f.conjugate().matrix() [ 1 0 0 0] [ 0 1 -1 -1] """
@cached_method def domain(self): """ Return the domain of this embedding.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: H.optimal_embeddings(-7, 2, R)[0].domain() Order in Number Field in a with defining polynomial x^2 + 7 """
# The following assumption is used, e.g., in the __call__ # method. I know that it is satisfied by the current # implementation. But somebody might someday annoying change # the implementation, and we want to catch that if it were to # ever happen.
def domain_gen(self): r""" Return the specific generator `c \sqrt{D}` for the domain order.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[0] sage: f.domain_gen() 2*a sage: f.domain_gen()^2 -28 """
def domain_conductor(self): """ Return the conductor of the domain.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: H.optimal_embeddings(-7, 2, R)[0].domain_conductor() 2 """
def beta(self): r""" Return the element `\beta` in the quaternion algebra order that `c\sqrt{D}` maps to.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: H.optimal_embeddings(-7, 2, R)[1].beta() -5*i + k """
def codomain(self): """ Return the codomain of this embedding.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: H.optimal_embeddings(-7, 2, R)[0].codomain() Order of Quaternion Algebra (-1, -3) with base ring Rational Field with basis (1/2 + 1/2*j + 7*k, 1/2*i + 13/2*k, j + 3*k, 11*k) """
@cached_method def _repr_(self): """ Return string representation of this embedding.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[1]; f._repr_() 'Embedding sending 2*sqrt(-7) to -5*i + k' """
def conjugate(self): """ Return the conjugate of this embedding, which is also an embedding.
EXAMPLES::
sage: H = heegner_points(11).reduce_mod(3); R = H.left_orders()[0] sage: f = H.optimal_embeddings(-7, 2, R)[1] sage: f.conjugate() Embedding sending 2*sqrt(-7) to 5*i - k sage: f Embedding sending 2*sqrt(-7) to -5*i + k """ self.__R, self.__beta.conjugate())
############################################################################# # Utility Functions #############################################################################
def quadratic_order(D, c, names='a'): """ Return order of conductor `c` in quadratic field with fundamental discriminant `D`.
INPUT:
- `D` -- fundamental discriminant
- `c` -- conductor
- ``names`` -- string (default: 'a')
OUTPUT:
- order `R` of conductor `c` in an imaginary quadratic field
- the element `c\sqrt{D}` as an element of `R`
The generator for the field is named 'a' by default.
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.quadratic_order(-7,3) (Order in Number Field in a with defining polynomial x^2 + 7, 3*a) sage: sage.schemes.elliptic_curves.heegner.quadratic_order(-7,3,'alpha') (Order in Number Field in alpha with defining polynomial x^2 + 7, 3*alpha) """
def class_number(D): """ Return the class number of the quadratic field with fundamental discriminant `D`.
INPUT:
- `D` -- integer
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.class_number(-20) 2 sage: sage.schemes.elliptic_curves.heegner.class_number(-23) 3 sage: sage.schemes.elliptic_curves.heegner.class_number(-163) 1
A ValueError is raised when `D` is not a fundamental discriminant::
sage: sage.schemes.elliptic_curves.heegner.class_number(-5) Traceback (most recent call last): ... ValueError: D (=-5) must be a fundamental discriminant """
def is_inert(D, p): r""" Return ``True`` if p is an inert prime in the field `\QQ(\sqrt{D})`.
INPUT:
- `D` -- fundamental discriminant
- `p` -- prime integer
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.is_inert(-7,3) True sage: sage.schemes.elliptic_curves.heegner.is_inert(-7,7) False sage: sage.schemes.elliptic_curves.heegner.is_inert(-7,11) False """
def is_split(D, p): r""" Return ``True`` if p is a split prime in the field `\QQ(\sqrt{D})`.
INPUT:
- `D` -- fundamental discriminant
- `p` -- prime integer
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.is_split(-7,3) False sage: sage.schemes.elliptic_curves.heegner.is_split(-7,7) False sage: sage.schemes.elliptic_curves.heegner.is_split(-7,11) True """
def is_ramified(D, p): r""" Return ``True`` if p is a ramified prime in the field `\QQ(\sqrt{D})`.
INPUT:
- `D` -- fundamental discriminant
- `p` -- prime integer
EXAMPLES::
sage: sage.schemes.elliptic_curves.heegner.is_ramified(-7,2) False sage: sage.schemes.elliptic_curves.heegner.is_ramified(-7,7) True sage: sage.schemes.elliptic_curves.heegner.is_ramified(-1,2) True """
def nearby_rational_poly(f, **kwds): r""" Return a polynomial whose coefficients are rational numbers close to the coefficients of `f`.
INPUT:
- `f` -- polynomial with real floating point entries
- ``**kwds`` -- passed on to ``nearby_rational`` method
EXAMPLES::
sage: R.<x> = RR[] sage: sage.schemes.elliptic_curves.heegner.nearby_rational_poly(2.1*x^2 + 3.5*x - 1.2, max_error=10e-16) 21/10*X^2 + 7/2*X - 6/5 sage: sage.schemes.elliptic_curves.heegner.nearby_rational_poly(2.1*x^2 + 3.5*x - 1.2, max_error=10e-17) 4728779608739021/2251799813685248*X^2 + 7/2*X - 5404319552844595/4503599627370496 sage: RR(4728779608739021/2251799813685248 - 21/10) 8.88178419700125e-17 """
def simplest_rational_poly(f, prec): """ Return a polynomial whose coefficients are as simple as possible rationals that are also close to the coefficients of f.
INPUT:
- `f` -- polynomial with real floating point entries
- ``prec`` -- positive integer
EXAMPLES::
sage: R.<x> = RR[] sage: sage.schemes.elliptic_curves.heegner.simplest_rational_poly(2.1*x^2 + 3.5*x - 1.2, 53) 21/10*X^2 + 7/2*X - 6/5 """
def satisfies_weak_heegner_hypothesis(N, D): r""" Check that `D` satisfies the weak Heegner hypothesis relative to `N`. This is all that is needed to define Heegner points.
The condition is that `D<0` is a fundamental discriminant and that each unramified prime dividing `N` splits in `K=\QQ(\sqrt{D})` and each ramified prime exactly divides `N`. We also do not require that `D<-4`.
INPUT:
- `N` -- positive integer
- `D` -- negative integer
EXAMPLES::
sage: s = sage.schemes.elliptic_curves.heegner.satisfies_weak_heegner_hypothesis sage: s(37,-7) True sage: s(37,-37) False sage: s(37,-37*4) True sage: s(100,-4) False sage: [D for D in [-1,-2,..,-40] if s(37,D)] [-3, -4, -7, -11, -40] sage: [D for D in [-1,-2,..,-100] if s(37,D)] [-3, -4, -7, -11, -40, -47, -67, -71, -83, -84, -95] sage: EllipticCurve('37a').heegner_discriminants_list(10) [-7, -11, -40, -47, -67, -71, -83, -84, -95, -104] """
def make_monic(f): r""" ``make_monic`` returns a monic integral polynomial `g` and an integer `d` such that if `\alpha` is a root of `g` then a root of `f` is `\alpha/d`.
INPUT:
- f -- polynomial over the rational numbers
EXAMPLES::
sage: R.<x> = QQ[] sage: sage.schemes.elliptic_curves.heegner.make_monic(3*x^3 + 14*x^2 - 7*x + 5) (x^3 + 14*x^2 - 21*x + 45, 3)
In this example we verify that make_monic does what we claim it does::
sage: K.<a> = NumberField(x^3 + 17*x - 3) sage: f = (a/7+2/3).minpoly(); f x^3 - 2*x^2 + 247/147*x - 4967/9261 sage: g, d = sage.schemes.elliptic_curves.heegner.make_monic(f) sage: g x^3 - 18522*x^2 + 144110421*x - 426000323007 sage: d 9261 sage: K.<b> = NumberField(g) sage: (b/d).minpoly() x^3 - 2*x^2 + 247/147*x - 4967/9261 """ # make f monic # find lcm of denominators
##################################################################### # Elliptic curve methods # Everywhere self below is an elliptic curve over QQ. #####################################################################
def ell_heegner_point(self, D, c=ZZ(1), f=None, check=True): """ Returns the Heegner point on this curve associated to the quadratic imaginary field `K=\QQ(\sqrt{D})`.
If the optional parameter `c` is given, returns the higher Heegner point associated to the order of conductor `c`.
INPUT:
- `D` -- a Heegner discriminant
- `c` -- (default: 1) conductor, must be coprime to `DN`
- `f` -- binary quadratic form or 3-tuple `(A,B,C)` of coefficients of `AX^2 + BXY + CY^2`
- ``check`` -- bool (default: ``True``)
OUTPUT:
The Heegner point `y_c`.
EXAMPLES::
sage: E = EllipticCurve('37a') sage: E.heegner_discriminants_list(10) [-7, -11, -40, -47, -67, -71, -83, -84, -95, -104] sage: P = E.heegner_point(-7); P # indirect doctest Heegner point of discriminant -7 on elliptic curve of conductor 37 sage: P.point_exact() (0 : 0 : 1) sage: P.curve() Elliptic Curve defined by y^2 + y = x^3 - x over Rational Field sage: P = E.heegner_point(-40).point_exact(); P (a : -a + 1 : 1) sage: P = E.heegner_point(-47).point_exact(); P (a : a^4 + a - 1 : 1) sage: P[0].parent() Number Field in a with defining polynomial x^5 - x^4 + x^3 + x^2 - 2*x + 1
Working out the details manually::
sage: P = E.heegner_point(-47).numerical_approx(prec=200) sage: f = algdep(P[0], 5); f x^5 - x^4 + x^3 + x^2 - 2*x + 1 sage: f.discriminant().factor() 47^2
The Heegner hypothesis is checked::
sage: E = EllipticCurve('389a'); P = E.heegner_point(-5,7); Traceback (most recent call last): ... ValueError: N (=389) and D (=-5) must satisfy the Heegner hypothesis
We can specify the quadratic form::
sage: P = EllipticCurve('389a').heegner_point(-7, 5, (778,925,275)); P Heegner point of discriminant -7 and conductor 5 on elliptic curve of conductor 389 sage: P.quadratic_form() 778*x^2 + 925*x*y + 275*y^2 """
def kolyvagin_point(self, D, c=ZZ(1), check=True): """ Returns the Kolyvagin point on this curve associated to the quadratic imaginary field `K=\QQ(\sqrt{D})` and conductor `c`.
INPUT:
- `D` -- a Heegner discriminant
- `c` -- (default: 1) conductor, must be coprime to `DN`
- ``check`` -- bool (default: ``True``)
OUTPUT:
The Kolyvagin point `P` of conductor `c`.
EXAMPLES::
sage: E = EllipticCurve('37a1') sage: P = E.kolyvagin_point(-67); P Kolyvagin point of discriminant -67 on elliptic curve of conductor 37 sage: P.numerical_approx() # abs tol 1e-14 (6.00000000000000 : -15.0000000000000 : 1.00000000000000) sage: P.index() 6 sage: g = E((0,-1,1)) # a generator sage: E.regulator() == E.regulator_of_points([g]) True sage: 6*g (6 : -15 : 1)
"""
def ell_heegner_discriminants(self, bound): """ Return the list of self's Heegner discriminants between -1 and -bound.
INPUT:
- ``bound (int)`` - upper bound for -discriminant
OUTPUT: The list of Heegner discriminants between -1 and -bound for the given elliptic curve.
EXAMPLES::
sage: E=EllipticCurve('11a') sage: E.heegner_discriminants(30) # indirect doctest [-7, -8, -19, -24] """ if self.satisfies_heegner_hypothesis(-D)]
def ell_heegner_discriminants_list(self, n): """ Return the list of self's first `n` Heegner discriminants smaller than -5.
INPUT:
- ``n (int)`` - the number of discriminants to compute
OUTPUT: The list of the first n Heegner discriminants smaller than -5 for the given elliptic curve.
EXAMPLES::
sage: E=EllipticCurve('11a') sage: E.heegner_discriminants_list(4) # indirect doctest [-7, -8, -19, -24] """
def heegner_point_height(self, D, prec=2, check_rank=True): r""" Use the Gross-Zagier formula to compute the Neron-Tate canonical height over `K` of the Heegner point corresponding to `D`, as an interval (it is computed to some precision using `L`-functions).
If the curve has rank at least 2, then the returned height is the exact Sage integer 0.
INPUT:
- ``D (int)`` - fundamental discriminant (=/= -3, -4)
- ``prec (int)`` - (default: 2), use `prec \cdot \sqrt(N) + 20` terms of `L`-series in computations, where `N` is the conductor.
- ``check_rank`` - whether to check if the rank is at least 2 by computing the Mordell-Weil rank directly.
OUTPUT: Interval that contains the height of the Heegner point.
EXAMPLES::
sage: E = EllipticCurve('11a') sage: E.heegner_point_height(-7) 0.22227?
Some higher rank examples::
sage: E = EllipticCurve('389a') sage: E.heegner_point_height(-7) 0 sage: E = EllipticCurve('5077a') sage: E.heegner_point_height(-7) 0 sage: E.heegner_point_height(-7,check_rank=False) 0.0000? """
raise ArithmeticError("Discriminant (=%s) must be a fundamental discriminant that satisfies the Heegner hypothesis."%D)
return IR(0) # rank even hence >= 2, so Heegner point is torsion.
# discriminant, etc., computed to this accuracy (which is easily the case). # this should be made more intelligent / rigorous relative # to the rest of the system.
else: # E has odd rank
def heegner_index(self, D, min_p=2, prec=5, descent_second_limit=12, verbose_mwrank=False, check_rank=True): r""" Return an interval that contains the index of the Heegner point `y_K` in the group of `K`-rational points modulo torsion on this elliptic curve, computed using the Gross-Zagier formula and/or a point search, or possibly half the index if the rank is greater than one.
If the curve has rank > 1, then the returned index is infinity.
.. NOTE::
If ``min_p`` is bigger than 2 then the index can be off by any prime less than ``min_p``. This function returns the index divided by `2` exactly when the rank of `E(K)` is greater than 1 and `E(\QQ)_{/tor} \oplus E^D(\QQ)_{/tor}` has index `2` in `E(K)_{/tor}`, where the second factor undergoes a twist.
INPUT:
- ``D (int)`` - Heegner discriminant
- ``min_p (int)`` - (default: 2) only rule out primes = min_p dividing the index.
- ``verbose_mwrank (bool)`` - (default: ``False``); print lots of mwrank search status information when computing regulator
- ``prec (int)`` - (default: 5), use prec\*sqrt(N) + 20 terms of L-series in computations, where N is the conductor.
- ``descent_second_limit`` - (default: 12)- used in 2-descent when computing regulator of the twist
- ``check_rank`` - whether to check if the rank is at least 2 by computing the Mordell-Weil rank directly.
OUTPUT: an interval that contains the index, or half the index
EXAMPLES::
sage: E = EllipticCurve('11a') sage: E.heegner_discriminants(50) [-7, -8, -19, -24, -35, -39, -40, -43] sage: E.heegner_index(-7) 1.00000?
::
sage: E = EllipticCurve('37b') sage: E.heegner_discriminants(100) [-3, -4, -7, -11, -40, -47, -67, -71, -83, -84, -95] sage: E.heegner_index(-95) # long time (1 second) 2.00000?
This tests doing direct computation of the Mordell-Weil group.
::
sage: EllipticCurve('675b').heegner_index(-11) 3.0000?
Currently discriminants -3 and -4 are not supported::
sage: E.heegner_index(-3) Traceback (most recent call last): ... ArithmeticError: Discriminant (=-3) must not be -3 or -4.
The curve 681b returns the true index, which is `3`::
sage: E = EllipticCurve('681b') sage: I = E.heegner_index(-8); I 3.0000?
In fact, whenever the returned index has a denominator of `2`, the true index is got by multiplying the returned index by `2`. Unfortunately, this is not an if and only if condition, i.e., sometimes the index must be multiplied by `2` even though the denominator is not `2`.
This example demonstrates the ``descent_second_limit`` option, which can be used to fine tune the 2-descent used to compute the regulator of the twist::
sage: E = EllipticCurve([1,-1,0,-1228,-16267]) sage: E.heegner_index(-8) Traceback (most recent call last): ... RuntimeError: ...
However when we search higher, we find the points we need::
sage: E.heegner_index(-8, descent_second_limit=16, check_rank=False) 2.00000?
Two higher rank examples (of ranks 2 and 3)::
sage: E = EllipticCurve('389a') sage: E.heegner_index(-7) +Infinity sage: E = EllipticCurve('5077a') sage: E.heegner_index(-7) +Infinity sage: E.heegner_index(-7, check_rank=False) 0.001? sage: E.heegner_index(-7, check_rank=False).lower() == 0 True """ raise ArithmeticError("Discriminant (=%s) must be a fundamental discriminant that satisfies the Heegner hypothesis."%D)
# First compute upper bound on height of Heegner point. return rings.infinity
# We divide by 2 to get the height **over Q** of the # Heegner point on the twist.
else: # Now rank(F) > 0
a = 2 else: FK_even_tor_pts.append(sum(FK_even_tor_pts)) if (z + T).is_divisible_by(2): a = 2; break
# Do naive search to eliminate possibility that Heegner point # is divisible by p<min_p, without finding Heegner point. return IR(1) else: FK_even_tor_pts.append(sum(FK_even_tor_pts))
def _adjust_heegner_index(self, a): r""" Take the square root of the interval that contains the Heegner index.
EXAMPLES::
sage: E = EllipticCurve('11a1') sage: a = RIF(sqrt(2))-1.4142135623730951 sage: E._adjust_heegner_index(a) 1.?e-8 """
def heegner_index_bound(self, D=0, prec=5, max_height=None): r""" Assume ``self`` has rank 0.
Return a list `v` of primes such that if an odd prime `p` divides the index of the Heegner point in the group of rational points modulo torsion, then `p` is in `v`.
If 0 is in the interval of the height of the Heegner point computed to the given prec, then this function returns `v = 0`. This does not mean that the Heegner point is torsion, just that it is very likely torsion.
If we obtain no information from a search up to ``max_height``, e.g., if the Siksek et al. bound is bigger than ``max_height``, then we return `v = -1`.
INPUT:
- ``D (int)`` - (default: 0) Heegner discriminant; if 0, use the first discriminant -4 that satisfies the Heegner hypothesis
- ``verbose (bool)`` - (default: ``True``)
- ``prec (int)`` - (default: 5), use `prec \cdot \sqrt(N) + 20` terms of `L`-series in computations, where `N` is the conductor.
- ``max_height (float)`` - should be = 21; bound on logarithmic naive height used in point searches. Make smaller to make this function faster, at the expense of possibly obtaining a worse answer. A good range is between 13 and 21.
OUTPUT:
- ``v`` - list or int (bad primes or 0 or -1)
- ``D`` - the discriminant that was used (this is useful if `D` was automatically selected).
- ``exact`` - either False, or the exact Heegner index (up to factors of 2)
EXAMPLES::
sage: E = EllipticCurve('11a1') sage: E.heegner_index_bound() ([2], -7, 2) """ else: raise RuntimeError("The rank must be 0.")
# First compute upper bound on Height of Heegner point. return 0, D, False else: break
verbose("No information by searching only up to max_height (=%s)."%c) return -1, D, False
""" We will use this function below in two places. It bounds the index using a nontrivial point. """
# Compute upper bound on square root of index. raise RuntimeError("Unable to compute bound for e=%s, D=%s (try increasing precision)"%(self, D))
# First try a quick search, in case we get lucky and find # a generator.
# Do search to eliminate possibility that Heegner point is # divisible by primes up to p, without finding Heegner point. P = F.point_search(c, rank_bound=1) P = [x for x in P if x.order() == rings.infinity] if len(P) == 0: # We've eliminated the possibility of a divisor up to p. return rings.prime_range(3, p), D, False else: return _bound(P)
################################################################################# def _heegner_index_in_EK(self, D): """ Return the index of the sum of `E(\QQ)/tor + E^D(\QQ)/tor` in `E(K)/tor`.
INPUT:
- `D` -- negative integer; the Heegner discriminant
OUTPUT:
a power of 2 -- the given index
EXAMPLES:
We compute the index for a rank 2 curve and found that it is 2::
sage: E = EllipticCurve('389a') sage: E._heegner_index_in_EK(-7) 2
We explicitly verify in the above example that indeed that index is divisible by 2 by writing down a generator of `E(\QQ)/tor + E^D(\QQ)/tor` that is divisible by 2 in `E(K)`::
sage: F = E.quadratic_twist(-7) sage: K = QuadraticField(-7,'a') sage: G = E.change_ring(K) sage: phi = F.change_ring(K).isomorphism_to(G) sage: P = G(E(-1,1)) + G((0,-1)) + G(phi(F(14,25))); P (-867/3872*a - 3615/3872 : -18003/170368*a - 374575/170368 : 1) sage: P.division_points(2) [(1/8*a + 5/8 : -5/16*a - 9/16 : 1)]
""" # check conditions, then use cache if possible. raise ValueError("D (=%s) must satisfy the Heegner hypothesis"%D) except KeyError: pass
##################################################################### # THE ALGORITHM: # # For an element P of an abelian group A, let [P] denote the # equivalence class of P in the quotient A/A_tor of A by # its torsion subgroup. Then for P in E(Q) + E^D(QQ), we # have that [P] is divisible by 2 in E(K)/tor if and only # there is R in E(K) such that 2*[R] = [P], and this is # only if there is R in E(K) and t in E(K)_tor such that # 2*R = P + t. # # Using complex conjugation, one sees that the quotient # group E(K)/tor / ( E(Q)/tor + E^D(Q)/tor ) is killed by 2. # So to compute the order of this group we run through # representatives P for A/(2A) where A = E(Q)/tor + E^D(Q)/tor, # and for each we see whether there is a torsion point t in E(K) # such that P + t is divisible by 2. Also, we have # 2 | P+t <==> 2 | P+n*t for any odd integer n, # so we may assume t is of 2-power order. #####################################################################
# Define a map phi that we'll use to put the points of E^D(QQ) # into E(K):
# Basis for E(Q)/tor oplus E^D(QQ)/tor in E(K): # Make a list of the 2-power order torsion points in E(K), including 0. ((z.order() % 2 == 0 and len(z.order().factor()) == 1))]
# Iterate through reps for A/(2*A) creating vectors in (1/2)*ZZ^r
# Take span of our vectors in (1/2)*ZZ^r, along with ZZ^r. This is E(K)/tor.
# Compute the index in E(K)/tor of A = E(Q)/tor + E^D(Q)/tor, cache, and return.
def heegner_sha_an(self, D, prec=53): r""" Return the conjectural (analytic) order of Sha for E over the field `K=\QQ(\sqrt{D})`.
INPUT:
- `D` -- negative integer; the Heegner discriminant
- prec -- integer (default: 53); bits of precision to compute analytic order of Sha
OUTPUT:
(floating point number) an approximation to the conjectural order of Sha.
.. NOTE::
Often you'll want to do ``proof.elliptic_curve(False)`` when using this function, since often the twisted elliptic curves that come up have enormous conductor, and Sha is nontrivial, which makes provably finding the Mordell-Weil group using 2-descent difficult.
EXAMPLES:
An example where E has conductor 11::
sage: E = EllipticCurve('11a') sage: E.heegner_sha_an(-7) # long time 1.00000000000000
The cache works::
sage: E.heegner_sha_an(-7) is E.heegner_sha_an(-7) # long time True
Lower precision::
sage: E.heegner_sha_an(-7,10) # long time 1.0
Checking that the cache works for any precision::
sage: E.heegner_sha_an(-7,10) is E.heegner_sha_an(-7,10) # long time True
Next we consider a rank 1 curve with nontrivial Sha over the quadratic imaginary field `K`; however, there is no Sha for `E` over `\QQ` or for the quadratic twist of `E`::
sage: E = EllipticCurve('37a') sage: E.heegner_sha_an(-40) # long time 4.00000000000000 sage: E.quadratic_twist(-40).sha().an() # long time 1 sage: E.sha().an() # long time 1
A rank 2 curve::
sage: E = EllipticCurve('389a') # long time sage: E.heegner_sha_an(-7) # long time 1.00000000000000
If we remove the hypothesis that `E(K)` has rank 1 in Conjecture 2.3 in [Gross-Zagier, 1986, page 311], then that conjecture is false, as the following example shows::
sage: E = EllipticCurve('65a') # long time sage: E.heegner_sha_an(-56) # long time 1.00000000000000 sage: E.torsion_order() # long time 2 sage: E.tamagawa_product() # long time 1 sage: E.quadratic_twist(-56).rank() # long time 2 """ # check conditions, then return from cache if possible. if not self.satisfies_heegner_hypothesis(D): raise ValueError("D (=%s) must satisfy the Heegner hypothesis"%D) try: return self.__heegner_sha_an[(D, prec)] except AttributeError: self.__heegner_sha_an = {} except KeyError: pass
# Use the BSD conjecture over the quadratic imaginary K -- # see page 311 of [Gross-Zagier, 1986] for the formula. E = self # notational convenience F = E.quadratic_twist(D).minimal_model() K = rings.QuadraticField(D, 'a')
# Compute each of the quantities in BSD # - The torsion subgroup over K. T = E.change_ring(K).torsion_order()
# - The product of the Tamagawa numbers, which because D is # coprime to N is just the square of the product of the # Tamagawa numbers over QQ for E. (we square below in the # BSD formula) cqprod = E.tamagawa_product()
# - The leading term of the L-series, as a product of two # other L-series. rE = E.rank() rF = F.rank() L_E = E.lseries().dokchitser(prec).derivative(1, rE) L_F = F.lseries().dokchitser(prec).derivative(1, rF) # NOTE: The binomial coefficient in the following formula # for the leading term in terms of the other two leading # terms comes from the product rule for the derivative. # You can think this through or just type something like # f = function('f',x); g = function('g',x); diff(f*g,6) # into Sage to be convinced. L = binomial(rE + rF, rE) * (L_E * L_F / factorial(rE+rF) )
# - ||omega||^2 -- the period. It is twice the volume of the # period lattice. See the following paper for a derivation: # "Verification of the Birch and Swinnerton-Dyer Conjecture # for Specific Elliptic Curves", G. Grigorov, A. Jorza, S. Patrikis, # C. Patrascu, W. Stein omega = 2 * abs(E.period_lattice().basis_matrix().det())
# - The regulator. # First we compute the regulator of the subgroup E(QQ) + E^D(QQ) # of E(K). The factor of 2 in the regulator # accounts for the fact that the height over K is twice the # height over QQ, i.e., for P in E(QQ) we have h_K(P,P) = # 2*h_Q(P,P). See, e.g., equation (6.4) on page 230 of # [Gross-Zagier, 1986]. Reg_prod = 2**(rE + rF) * E.regulator(precision=prec) * F.regulator(precision=prec) # Next we call off to the _heegner_index_in_EK function, which # saturates the group E(QQ) + E^D(QQ) in E(K), given us the index, # which must be a power of 2, since E(QQ) is the +1 eigenspace for # complex conjugation, and E^D(QQ) is the -1 eigenspace. ind = self._heegner_index_in_EK(D) # Finally, we know the regulator of E(K). Reg = Reg_prod / ind**2
# - Square root of the absolute value of the discriminant. This is # easy; we just make sure the D passed in is an integer, so we # can call sqrt with the chosen precision. sqrtD = ZZ(abs(D)).sqrt(prec=prec)
# - Done: Finally, we plug everything into the BSD formula to get the # analytic order of Sha. sha_an = (L * T**2 * sqrtD) / (omega * Reg * cqprod**2)
# - We cache and return the answer. self.__heegner_sha_an[(D, prec)] = sha_an return sha_an
def _heegner_forms_list(self, D, beta=None, expected_count=None): """ Returns a list of quadratic forms corresponding to Heegner points with discriminant `D` and a choice of `\beta` a square root of `D` mod `4N`. Specifically, given a quadratic form `f = Ax^2 + Bxy + Cy^2` we let `\tau_f` be a root of `Ax^2 + Bx + C` and the discriminant `\Delta(\tau_f) = \Delta(f) = D` must be invariant under multiplication by `N`, the conductor of ``self``.
`\Delta(N\tau_f) = \Delta(\tau_f) = \Delta(f) = D`
EXAMPLES::
sage: E = EllipticCurve('37a') sage: E._heegner_forms_list(-7) [37*x^2 + 17*x*y + 2*y^2] sage: E._heegner_forms_list(-195) [37*x^2 + 29*x*y + 7*y^2, 259*x^2 + 29*x*y + y^2, 111*x^2 + 177*x*y + 71*y^2, 2627*x^2 + 177*x*y + 3*y^2] sage: E._heegner_forms_list(-195)[-1].discriminant() -195 sage: len(E._heegner_forms_list(-195)) 4 sage: QQ[sqrt(-195)].class_number() 4
sage: E = EllipticCurve('389a') sage: E._heegner_forms_list(-7) [389*x^2 + 185*x*y + 22*y^2] sage: E._heegner_forms_list(-59) [389*x^2 + 313*x*y + 63*y^2, 1167*x^2 + 313*x*y + 21*y^2, 3501*x^2 + 313*x*y + 7*y^2] """ else: assert beta**2 == Integers(4*N)(D) # Note: This may give a sub-optimal list of forms.
def _heegner_best_tau(self, D, prec=None): r""" Given a discriminant `D`, find the Heegner point `\tau` in the upper half plane with largest imaginary part (which is optimal for evaluating the modular parametrization). If the optional parameter ``prec`` is given, return `\tau` to ``prec`` bits of precision, otherwise return it exactly as a symbolic object.
EXAMPLES::
sage: E = EllipticCurve('37a') sage: E._heegner_best_tau(-7) 1/74*sqrt(-7) - 17/74 sage: EllipticCurve('389a')._heegner_best_tau(-11) 1/778*sqrt(-11) - 355/778 sage: EllipticCurve('389a')._heegner_best_tau(-11, prec=100) -0.45629820051413881748071979434 + 0.0042630138693514136878083968338*I """ # We know that N|A, so A = N is optimal. # TODO: make sure a different choice of b is not better?
def satisfies_heegner_hypothesis(self, D): """ Returns ``True`` precisely when `D` is a fundamental discriminant that satisfies the Heegner hypothesis for this elliptic curve.
EXAMPLES::
sage: E = EllipticCurve('11a1') sage: E.satisfies_heegner_hypothesis(-7) True sage: E.satisfies_heegner_hypothesis(-11) False """
##################################################################### # End of elliptic curve methods. ##################################################################### |