class VectorValuedModularForms(SageObject):
r"""
Class representing a space of vector valued modular forms
transforming with the Weil representation of a discriminant module.
EXAMPLES:
As input we use any input that one can use for a finite quadratic module.
(For instance a genus symbol.)
::
sage: V=VectorValuedModularForms('2_7^+1.3^-2')
sage: V
Vector valued modular forms for the Weil representation corresponding to:
Finite quadratic module in 3 generators:
gens: e0, e1, e2
form: 3/4*x0^2 + 2/3*x1^2 + 1/3*x2^2
SEE ALSO:
:class:`psage.modules.finite_quadratic_modules.FiniteQuadraticModule`
"""
def __init__(self,
A,
use_genus_symbols=False,
aniso_formula=False,
use_reduction=False):
try:
from sfqm.fqm.genus_symbol import GenusSymbol
except ImportError as e:
print(e)
use_genus_symbols = False
print("Not using genus symbols.")
self._use_reduction = use_reduction
if use_genus_symbols:
if isinstance(A, str):
g = GenusSymbol(A)
else:
try:
g = GenusSymbol(A.jordan_decomposition().genus_symbol())
except:
raise ValueError
self._g = g
n2 = self._n2 = g.torsion(2)
self._v2 = g.two_torsion_values()
self._M = None
self._aniso_formula = aniso_formula
else:
self._M = FiniteQuadraticModule(A)
self._g = None
self._level = self._M.level()
self._aniso_formula = False
if is_odd(self._M.order()):
self._n2 = n2 = 1
self._v2 = {0: 1}
else:
self._M2 = M2 = self._M.kernel_subgroup(2).as_ambient()[0]
self._n2 = n2 = self._M2.order()
self._v2 = list(self._M2.values())
if use_genus_symbols:
self._signature = g.signature()
m = g.order()
else:
self._signature = self._M.signature()
m = self._M.order()
self._m = m
d = Integer(1) / Integer(2) * (m + n2) # |discriminant group/{+/-1}|
self._d = d
self._alpha3 = None
self._alpha4 = None
def __repr__(self):
return "Vector valued modular forms for the Weil representation corresponding to: \n" + self._M.__repr__(
)
def finite_quadratic_module(self):
return self._M
def dimension(self, k, ignore=False, debug=0):
if k < 2 and not ignore:
raise NotImplementedError("k has to >= 2")
s = self._signature
if not (2 * k in ZZ):
raise ValueError("k has to be integral or half-integral")
if (2 * k + s) % 4 != 0 and not ignore:
raise NotImplementedError(
"2k has to be congruent to -signature mod 4")
if 0 in self._v2:
v2 = self._v2[0]
else:
v2 = 1
if self._g != None:
if not self._aniso_formula:
vals = list(self._g.values())
#else:
#print "using aniso_formula"
M = self._g
else:
vals = list(self._M.values())
M = self._M
prec = ceil(max(log(M.order(), 2), 52) + 1) + 17
#print prec
RR = RealField(prec)
CC = ComplexField(prec)
d = self._d
m = self._m
if debug > 0: print(d, m)
if self._alpha3 == None:
if self._aniso_formula:
self._alpha4 = 1
self._alpha3 = -sum(
[BB(a) * mm for a, mm in self._v2.items() if a != 0])
#print self._alpha3
self._alpha3 += Integer(d) - Integer(
1) - self._g.beta_formula()
#print self._alpha3, self._g.a5prime_formula()
self._alpha3 = self._alpha3 / RR(2)
else:
self._alpha3 = sum([(1 - a) * mm for a, mm in self._v2.items()
if a != 0])
#print self._alpha3
self._alpha3 += sum([(1 - a) * mm for a, mm in vals.items()
if a != 0])
#print self._alpha3
self._alpha3 = self._alpha3 / Integer(2)
self._alpha4 = 1 / Integer(2) * (
vals[0] + v2) # the codimension of SkL in MkL
alpha3 = self._alpha3
alpha4 = self._alpha4
if debug > 0: print(alpha3, alpha4)
g1 = M.char_invariant(1)
g1 = CC(g1[0] * g1[1])
#print g1
g2 = M.char_invariant(2)
g2 = RR(real(g2[0] * g2[1]))
if debug > 0: print(g2, g2.parent())
g3 = M.char_invariant(-3)
g3 = CC(g3[0] * g3[1])
if debug > 0:
print(
RR(d) / RR(4),
sqrt(RR(m)) / RR(4),
CC(exp(2 * CC.pi() * CC(0, 1) * (2 * k + s) / Integer(8))))
alpha1 = RR(d) / RR(4) - (sqrt(RR(m)) / RR(4) * CC(
exp(2 * CC.pi() * CC(0, 1) * (2 * k + s) / Integer(8))) * g2)
if debug > 0: print(alpha1)
alpha2 = RR(d) / RR(3) + sqrt(RR(m)) / (3 * sqrt(RR(3))) * real(
exp(CC(2 * CC.pi() * CC(0, 1) * (4 * k + 3 * s - 10) / 24)) *
(g1 + g3))
if debug > 0: print(alpha1, alpha2, g1, g2, g3, d, k, s)
dim = real(d + (d * k / Integer(12)) - alpha1 - alpha2 - alpha3)
if debug > 0:
print("dimension:", dim)
if abs(dim - round(dim)) > 1e-6:
raise RuntimeError(
"Error ({0}) too large in dimension formula for {1} and k={2}".
format(abs(dim - round(dim)),
self._M if self._M is not None else self._g, k))
dimr = dim
dim = Integer(round(dim))
if k >= 2 and dim < 0:
raise RuntimeError("Negative dimension (= {0}, {1})!".format(
dim, dimr))
return dim
def dimension_cusp_forms(self,
k,
ignore=False,
no_inv=False,
test_positive=False,
proof=False,
debug=1):
if debug > 0:
if self._g is not None:
print("Computing dimension for {}".format(self._g))
else:
print("Computing dimension for {}".format(self._M))
if k == Integer(3) / 2:
dim = self.dimension(k, True, debug=debug) - self._alpha4
if not test_positive or dim <= 0:
if self._M == None:
self._M = self._g.finite_quadratic_module()
corr = weight_one_half_dim(self._M,
self._use_reduction,
proof=proof)
if debug > 0: print("weight one half: {0}".format(corr))
dim += corr
else:
dim = self.dimension(k, ignore, debug=debug) - self._alpha4
if k == Integer(2) and not no_inv:
if test_positive and dim > 0:
return dim
if self._M == None:
self._M = self._g.finite_quadratic_module()
if self._M.level() == 1:
return dim + 1
dinv = cython_invariants_dim(self._M, self._use_reduction)
dim = dim + dinv
if dim < 0:
raise RuntimeError(
"Negative dimension (= {0}, alpha4 = {1})!".format(
dim, self._alpha4))
return dim
