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# -*- coding: utf-8 -*- 

r""" 

`p`-adic `L`-series attached to overconvergent eigensymbols 

 

An overconvergent eigensymbol gives rise to a `p`-adic `L`-series, 

which is essentially defined as the evaluation of the eigensymbol at the 

path `0 \rightarrow \infty`. The resulting distribution on `\ZZ_p` can be restricted 

to `\ZZ_p^\times`, thus giving the measure attached to the sought `p`-adic `L`-series. 

All this is carefully explained in [PS]_. 

 

""" 

#***************************************************************************** 

# Copyright (C) 2012 Robert Pollack <rpollack@math.bu.edu> 

# 

# Distributed under the terms of the GNU General Public License (GPL) 

# 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 

from __future__ import absolute_import 

from sage.rings.padics.all import pAdicField 

from sage.rings.all import ZZ, QQ 

from sage.rings.power_series_ring import PowerSeriesRing 

from sage.rings.big_oh import O 

from sage.arith.all import binomial, gcd, kronecker 

from sage.rings.padics.precision_error import PrecisionError 

 

from sage.structure.sage_object import SageObject 

from .sigma0 import Sigma0 

from .fund_domain import M2Z 

 

 

class pAdicLseries(SageObject): 

r""" 

The `p`-adic `L`-series associated to an overconvergent eigensymbol. 

 

INPUT: 

 

- ``symb`` -- an overconvergent eigensymbol 

- ``gamma`` -- topological generator of `1 + p\ZZ_p` (default: `1+p` or 5 if `p=2`) 

- ``quadratic_twist`` -- conductor of quadratic twist `\chi` (default: 1) 

- ``precision`` -- if None (default) is specified, the correct precision bound is 

computed and the answer is returned modulo that accuracy 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('37a') 

sage: p = 5 

sage: prec = 4 

sage: L = E.padic_lseries(p, implementation="pollackstevens", precision=prec) # long time 

sage: L[1] # long time 

1 + 4*5 + 2*5^2 + O(5^3) 

sage: L.series(3) # long time 

O(5^4) + (1 + 4*5 + 2*5^2 + O(5^3))*T + (3 + O(5^2))*T^2 + O(T^3) 

 

:: 

 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: E = EllipticCurve('20a') 

sage: phi = E.pollack_stevens_modular_symbol() 

sage: Phi = phi.p_stabilize_and_lift(3, 4) # long time 

sage: L = pAdicLseries(Phi) # long time 

sage: L.series(4) # long time 

2*3 + O(3^4) + (3 + O(3^2))*T + (2 + O(3))*T^2 + O(3^0)*T^3 + O(T^4) 

 

An example of a `p`-adic `L`-series associated to a modular 

abelian surface. This is not tested as it takes too long.:: 

 

sage: from sage.modular.pollack_stevens.space import ps_modsym_from_simple_modsym_space 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: A = ModularSymbols(103,2,1).cuspidal_submodule().new_subspace().decomposition()[0] 

sage: p = 19 

sage: prec = 4 

sage: phi = ps_modsym_from_simple_modsym_space(A) 

sage: ap = phi.Tq_eigenvalue(p,prec) 

sage: c1,c2 = phi.completions(p,prec) 

sage: phi1,psi1 = c1 

sage: phi2,psi2 = c2 

sage: phi1p = phi1.p_stabilize_and_lift(p,ap = psi1(ap), M = prec) # not tested - too long 

sage: L1 = pAdicLseries(phi1p) # not tested - too long 

sage: phi2p = phi2.p_stabilize_and_lift(p,ap = psi2(ap), M = prec) # not tested - too long 

sage: L2 = pAdicLseries(phi2p) # not tested - too long 

sage: L1[1]*L2[1] # not tested - too long 

13 + 9*19 + 18*19^2 + O(19^3) 

""" 

 

def __init__(self, symb, gamma=None, quadratic_twist=1, precision=None): 

r""" 

Initialize the class 

 

EXAMPLES:: 

 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: E = EllipticCurve('11a3') 

sage: phi = E.pollack_stevens_modular_symbol() 

sage: p = 11 

sage: prec = 3 

sage: Phi = phi.lift(p, prec,eigensymbol=True) # long time 

sage: L = pAdicLseries(Phi) # long time 

sage: L.series(3) # long time 

O(11^3) + (2 + 5*11 + O(11^2))*T + (10 + O(11))*T^2 + O(T^3) 

 

sage: TestSuite(L).run() # long time 

""" 

self._coefficients = {} 

 

if symb.parent().prime() is None: 

raise ValueError("Not a p-adic overconvergent modular symbol.") 

 

self._symb = symb 

 

if gamma is None: 

p = self._symb.parent().prime() 

if p == 2: 

gamma = 1 + 4 

else: 

gamma = 1 + self._symb.parent().prime() 

 

self._gamma = gamma 

self._quadratic_twist = quadratic_twist 

self._precision = precision 

self._cinf = ZZ(1) # is set when called for an elliptic curve 

 

def __getitem__(self, n): 

r""" 

Return the `n`-th coefficient of the `p`-adic `L`-series 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('14a5') 

sage: L = E.padic_lseries(7,implementation="pollackstevens",precision=5) # long time 

sage: L[0] # long time 

O(7^5) 

sage: L[1] # long time 

5 + 5*7 + 2*7^2 + 2*7^3 + O(7^4) 

""" 

 

if n in self._coefficients: 

return self._coefficients[n] 

else: 

p = self.prime() 

symb = self.symbol() 

# ap = symb.Tq_eigenvalue(p) 

gamma = self._gamma 

precision = self._precision 

 

S = QQ[['z']] 

z = S.gen() 

M = symb.precision_relative() 

K = pAdicField(p, M) 

dn = 0 

if n == 0: 

precision = M 

lb = [1] + [0 for a in range(M - 1)] 

else: 

lb = log_gamma_binomial(p, gamma, z, n, 2 * M) 

if precision is None: 

precision = min([j + lb[j].valuation(p) 

for j in range(M, len(lb))]) 

lb = [lb[a] for a in range(M)] 

 

for j in range(len(lb)): 

cjn = lb[j] 

temp = sum((ZZ(K.teichmuller(a)) ** (-j)) 

* self._basic_integral(a, j) for a in range(1, p)) 

dn = dn + cjn * temp 

self._coefficients[n] = dn.add_bigoh(precision) 

self._coefficients[n] /= self._cinf 

return self._coefficients[n] 

 

def __eq__(self, other): 

r""" 

Compare ``self`` and ``other``. 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('11a') 

sage: L = E.padic_lseries(11,implementation="pollackstevens",precision=6) # long time 

sage: L == loads(dumps(L)) # indirect doctest long time 

True 

""" 

if not isinstance(other, pAdicLseries): 

return False 

 

return (self._symb == other._symb and 

self._quadratic_twist == other._quadratic_twist and 

self._gamma == other._gamma and 

self._precision == other._precision) 

 

def __ne__(self, other): 

r""" 

Compare ``self`` and ``other``. 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('11a') 

sage: L = E.padic_lseries(11,implementation="pollackstevens",precision=6) # long time 

sage: L != L # long time 

False 

""" 

return not self.__eq__(other) 

 

def symbol(self): 

r""" 

Return the overconvergent modular symbol 

 

EXAMPLES:: 

 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: E = EllipticCurve('21a4') 

sage: phi = E.pollack_stevens_modular_symbol() 

sage: Phi = phi.p_stabilize_and_lift(2,5) # long time 

sage: L = pAdicLseries(Phi) # long time 

sage: L.symbol() # long time 

Modular symbol of level 42 with values in Space of 2-adic distributions with k=0 action and precision cap 15 

sage: L.symbol() is Phi # long time 

True 

""" 

return self._symb 

 

def prime(self): 

r""" 

Return the prime `p` as in `p`-adic `L`-series. 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('19a') 

sage: L = E.padic_lseries(19, implementation="pollackstevens",precision=6) # long time 

sage: L.prime() # long time 

19 

""" 

return self._symb.parent().prime() 

 

def quadratic_twist(self): 

r""" 

Return the discriminant of the quadratic twist 

 

EXAMPLES:: 

 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: E = EllipticCurve('37a') 

sage: phi = E.pollack_stevens_modular_symbol() 

sage: Phi = phi.lift(37,4) 

sage: L = pAdicLseries(Phi, quadratic_twist=-3) 

sage: L.quadratic_twist() 

-3 

""" 

return self._quadratic_twist 

 

def _repr_(self): 

r""" 

Return the string representation 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('14a2') 

sage: L = E.padic_lseries(3, implementation="pollackstevens", precision=4) # long time 

sage: L._repr_() # long time 

'3-adic L-series of Modular symbol of level 42 with values in Space of 3-adic distributions with k=0 action and precision cap 8' 

""" 

return "%s-adic L-series of %s" % (self.prime(), self.symbol()) 

 

def series(self, prec=5): 

r""" 

Return the ``prec``-th approximation to the `p`-adic `L`-series 

associated to self, as a power series in `T` (corresponding to 

`\gamma-1` with `\gamma` the chosen generator of `1+p\ZZ_p`). 

 

INPUT: 

 

- ``prec`` -- (default 5) is the precision of the power series 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('14a2') 

sage: p = 3 

sage: prec = 6 

sage: L = E.padic_lseries(p,implementation="pollackstevens",precision=prec) # long time 

sage: L.series(4) # long time 

2*3 + 3^4 + 3^5 + O(3^6) + (2*3 + 3^2 + O(3^4))*T + (2*3 + O(3^2))*T^2 + (3 + O(3^2))*T^3 + O(T^4) 

 

sage: E = EllipticCurve("15a3") 

sage: L = E.padic_lseries(5,implementation="pollackstevens",precision=15) # long time 

sage: L.series(3) # long time 

O(5^15) + (2 + 4*5^2 + 3*5^3 + 5^5 + 2*5^6 + 3*5^7 + 3*5^8 + 2*5^9 + 2*5^10 + 3*5^11 + 5^12 + O(5^13))*T + (4*5 + 4*5^3 + 3*5^4 + 4*5^5 + 3*5^6 + 2*5^7 + 5^8 + 4*5^9 + 3*5^10 + O(5^11))*T^2 + O(T^3) 

 

sage: E = EllipticCurve("79a1") 

sage: L = E.padic_lseries(2,implementation="pollackstevens",precision=10) # not tested 

sage: L.series(4) # not tested 

O(2^9) + (2^3 + O(2^4))*T + O(2^0)*T^2 + (O(2^-3))*T^3 + O(T^4) 

""" 

p = self.prime() 

M = self.symbol().precision_relative() 

K = pAdicField(p, M) 

R = PowerSeriesRing(K, names='T') 

T = R.gens()[0] 

return R([self[i] for i in range(prec)]).add_bigoh(prec) 

 

def interpolation_factor(self, ap, chip=1, psi=None): 

r""" 

Return the interpolation factor associated to self. 

This is the `p`-adic multiplier that which appears in 

the interpolation formula of the `p`-adic `L`-function. It 

has the form `(1-\alpha_p^{-1})^2`, where `\alpha_p` is the 

unit root of `X^2 - \psi(a_p) \chi(p) X + p`. 

 

INPUT: 

 

- ``ap`` -- the eigenvalue of the Up operator 

 

- ``chip`` -- the value of the nebentype at p (default: 1) 

 

- ``psi`` -- a twisting character (default: None) 

 

OUTPUT: a `p`-adic number 

 

EXAMPLES:: 

 

sage: E = EllipticCurve('19a2') 

sage: L = E.padic_lseries(3,implementation="pollackstevens",precision=6) # long time 

sage: ap = E.ap(3) # long time 

sage: L.interpolation_factor(ap) # long time 

3^2 + 3^3 + 2*3^5 + 2*3^6 + O(3^7) 

 

Comparing against a different implementation:: 

 

sage: L = E.padic_lseries(3) 

sage: (1-1/L.alpha(prec=4))^2 

3^2 + 3^3 + O(3^5) 

""" 

M = self.symbol().precision_relative() 

p = self.prime() 

if p == 2: 

R = pAdicField(2, M + 1) 

else: 

R = pAdicField(p, M) 

if psi is not None: 

ap = psi(ap) 

ap = ap * chip 

sdisc = R(ap ** 2 - 4 * p).sqrt() 

v0 = (R(ap) + sdisc) / 2 

v1 = (R(ap) - sdisc) / 2 

if v0.valuation() > 0: 

v0, v1 = v1, v0 

alpha = v0 

return (1 - 1 / alpha) ** 2 

 

def _basic_integral(self, a, j): 

r""" 

Return `\int_{a+pZ_p} (z-{a})^j d\Phi(0-infty)` 

-- see formula [Pollack-Stevens, sec 9.2] 

 

INPUT: 

 

- ``a`` -- integer in range(p) 

- ``j`` -- integer in range(self.symbol().precision_relative()) 

 

EXAMPLES:: 

 

sage: from sage.modular.pollack_stevens.padic_lseries import pAdicLseries 

sage: E = EllipticCurve('11a3') 

sage: L = E.padic_lseries(5, implementation="pollackstevens", precision=4) #long time 

sage: L._basic_integral(1,2) # long time 

2*5^2 + 5^3 + O(5^4) 

""" 

symb = self.symbol() 

M = symb.precision_relative() 

if j > M: 

raise PrecisionError("Too many moments requested") 

p = self.prime() 

ap = symb.Tq_eigenvalue(p) 

D = self._quadratic_twist 

ap = ap * kronecker(D, p) 

K = pAdicField(p, M) 

symb_twisted = symb.evaluate_twisted(a, D) 

return ( sum(binomial(j, r) 

* ((a - ZZ(K.teichmuller(a))) ** (j - r)) 

* (p ** r) 

* symb_twisted.moment(r) for r in range(j + 1)) 

/ ap ) 

 

 

def log_gamma_binomial(p, gamma, z, n, M): 

r""" 

Return the list of coefficients in the power series 

expansion (up to precision `M`) of `\binom{\log_p(z)/\log_p(\gamma)}{n}` 

 

INPUT: 

 

- ``p`` -- prime 

- ``gamma`` -- topological generator, e.g. `1+p` 

- ``z`` -- variable 

- ``n`` -- nonnegative integer 

- ``M`` -- precision 

 

OUTPUT: 

 

The list of coefficients in the power series expansion of 

`\binom{\log_p(z)/\log_p(\gamma)}{n}` 

 

EXAMPLES:: 

 

sage: R.<z> = QQ['z'] 

sage: from sage.modular.pollack_stevens.padic_lseries import log_gamma_binomial 

sage: log_gamma_binomial(5,1+5,z,2,4) 

[0, -3/205, 651/84050, -223/42025] 

sage: log_gamma_binomial(5,1+5,z,3,4) 

[0, 2/205, -223/42025, 95228/25845375] 

""" 

L = sum([ZZ(-1) ** j / j * z ** j for j in range(1, M)]) # log_p(1+z) 

loggam = L / (L(gamma - 1)) # log_{gamma}(1+z)= log_p(1+z)/log_p(gamma) 

return z.parent()(binomial(loggam, n)).truncate(M).list()