# Numerical computation of newforms¶

class sage.modular.modform.numerical.NumericalEigenforms(group, weight=2, eps=1e-20, delta=0.01, tp=[2, 3, 5])

numerical_eigenforms(group, weight=2, eps=1e-20, delta=1e-2, tp=[2,3,5])

INPUT:

• group - a congruence subgroup of a Dirichlet character of order 1 or 2
• weight - an integer >= 2
• eps - a small float; abs( ) < eps is what “equal to zero” is interpreted as for floating point numbers.
• delta - a small-ish float; eigenvalues are considered distinct if their difference has absolute value at least delta
• tp - use the Hecke operators T_p for p in tp when searching for a random Hecke operator with distinct Hecke eigenvalues.

OUTPUT:

A numerical eigenforms object, with the following useful methods:

• ap() - return all eigenvalues of $$T_p$$

• eigenvalues() - list of eigenvalues corresponding to the given list of primes, e.g.,:

[[eigenvalues of T_2],
[eigenvalues of T_3],
[eigenvalues of T_5], ...]

• systems_of_eigenvalues() - a list of the systems of eigenvalues of eigenforms such that the chosen random linear combination of Hecke operators has multiplicity 1 eigenvalues.

EXAMPLES:

sage: n = numerical_eigenforms(23)
True
sage: n.ap(2)  # rel tol 2e-15
[3.0, 0.6180339887498941, -1.618033988749895]
sage: n.systems_of_eigenvalues(7)  # rel tol 2e-15
[
[-1.618033988749895, 2.23606797749979, -3.23606797749979],
[0.6180339887498941, -2.2360679774997902, 1.2360679774997883],
[3.0, 4.0, 6.0]
]
sage: n.systems_of_abs(7)
[
[0.6180339887..., 2.236067977..., 1.236067977...],
[1.6180339887..., 2.236067977..., 3.236067977...],
[3.0, 4.0, 6.0]
]
sage: n.eigenvalues([2,3,5])  # rel tol 2e-15
[[3.0, 0.6180339887498941, -1.618033988749895],
[4.0, -2.2360679774997902, 2.23606797749979],
[6.0, 1.2360679774997883, -3.23606797749979]]

ap(p)

Return a list of the eigenvalues of the Hecke operator $$T_p$$ on all the computed eigenforms. The eigenvalues match up between one prime and the next.

INPUT:

• p - integer, a prime number

OUTPUT:

• list - a list of double precision complex numbers

EXAMPLES:

sage: n = numerical_eigenforms(11,4)
sage: n.ap(2) # random order
[9.0, 9.0, 2.73205080757, -0.732050807569]
sage: n.ap(3) # random order
[28.0, 28.0, -7.92820323028, 5.92820323028]
sage: m = n.modular_symbols()
sage: x = polygen(QQ, 'x')
sage: m.T(2).charpoly('x').factor()
(x - 9)^2 * (x^2 - 2*x - 2)
sage: m.T(3).charpoly('x').factor()
(x - 28)^2 * (x^2 + 2*x - 47)

eigenvalues(primes)

Return the eigenvalues of the Hecke operators corresponding to the primes in the input list of primes. The eigenvalues match up between one prime and the next.

INPUT:

• primes - a list of primes

OUTPUT:

list of lists of eigenvalues.

EXAMPLES:

sage: n = numerical_eigenforms(1,12)
sage: n.eigenvalues([3,5,13])  # rel tol 2e-10
[[177148.0, 252.00000000001896], [48828126.0, 4830.000000001376], [1792160394038.0, -577737.9999898539]]

level()

Return the level of this set of modular eigenforms.

EXAMPLES:

sage: n = numerical_eigenforms(61) ; n.level()
61

modular_symbols()

Return the space of modular symbols used for computing this set of modular eigenforms.

EXAMPLES:

sage: n = numerical_eigenforms(61) ; n.modular_symbols()
Modular Symbols space of dimension 5 for Gamma_0(61) of weight 2 with sign 1 over Rational Field

systems_of_abs(bound)

Return the absolute values of all systems of eigenvalues for self for primes up to bound.

EXAMPLES:

sage: numerical_eigenforms(61).systems_of_abs(10)  # rel tol 6e-14
[
[0.3111078174659775, 2.903211925911551, 2.525427560843529, 3.214319743377552],
[1.0, 2.0000000000000027, 3.000000000000003, 1.0000000000000044],
[1.4811943040920152, 0.8060634335253695, 3.1563251746586642, 0.6751308705666477],
[2.170086486626034, 1.7092753594369208, 1.63089761381512, 0.46081112718908984],
[3.0, 4.0, 6.0, 8.0]
]

systems_of_eigenvalues(bound)

Return all systems of eigenvalues for self for primes up to bound.

EXAMPLES:

sage: numerical_eigenforms(61).systems_of_eigenvalues(10)  # rel tol 6e-14
[
[-1.4811943040920152, 0.8060634335253695, 3.1563251746586642, 0.6751308705666477],
[-1.0, -2.0000000000000027, -3.000000000000003, 1.0000000000000044],
[0.3111078174659775, 2.903211925911551, -2.525427560843529, -3.214319743377552],
[2.170086486626034, -1.7092753594369208, -1.63089761381512, -0.46081112718908984],
[3.0, 4.0, 6.0, 8.0]
]

weight()

Return the weight of this set of modular eigenforms.

EXAMPLES:

sage: n = numerical_eigenforms(61) ; n.weight()
2

sage.modular.modform.numerical.support(v, eps)

Given a vector $$v$$ and a threshold eps, return all indices where $$|v|$$ is larger than eps.

EXAMPLES:

sage: sage.modular.modform.numerical.support( numerical_eigenforms(61)._easy_vector(), 1.0 )
[]

sage: sage.modular.modform.numerical.support( numerical_eigenforms(61)._easy_vector(), 0.5 )
[0, 1]


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