On the image of code polynomials under theta map

Theta Series of Unimodular Lattices, Combinatorial Identities and Weighted Symmetric Polynomials

We find two combinatorial identities on the theta series of the root lattices of the finite-dimensional simple Lie algebras of type $D_{4n}$ and the cosets in their integral duals, in terms of the well-known Essenstein series $E_4(z)$ and Ramanujan series $\Dlt_{24}(z)$. Using these two identities, we determine the theta series of certain infinite families of postive definite even unimodular lattices obtained by gluing finite copies of the root lattices of the finite-dimensional simple Lie algebras of type $D_{2n}$. It turns out that these theta series are weighted symmetric polynomials of two…

Seesaw Identities and Theta Contractions with Generalized Theta Functions, and Restrictions of Theta Lifts

We prove a seesaw identity for theta functions with polynomials, and establish a formula for the corresponding theta contractions. We then use it to determine the restrictions of theta lifts to sub-Grassmannians, with some applications.

An algebraic property of Hecke operators and two indefinite theta series

We prove an algebraic property of the elements defining Hecke operators on period polynomials associated with modular forms, which implies that the pairing on period polynomials corresponding to the Petersson scalar product of modular forms is Hecke equivariant. As a consequence of this proof, we derive two indefinite theta series identities which can be seen as analogues of Jacobi's formula for the theta series associated with the sum of four squares.

A quasi-linear time algorithm for computing modular polynomials in dimension 2

We propose to generalize the work of Régis Dupont for computing modular polynomials in dimension $2$ to new invariants. We describe an algorithm to compute modular polynomials for invariants derived from theta constants and prove under some heuristics that this algorithm is quasi-linear in its output size. Some properties of the modular polynomials defined from quotients of theta constants are analyzed. We report on experiments with our implementation.

Quadratic forms and their theta series - infinitesimal aspects

We study the theta map which assigns to a real quadratic form its theta series. We introduce two invariants reflecting whether the differential of the theta map vanishes or is degenerate. We provide examples of lattices where this differential is zero. These invariants turn out to be modular forms for integral lattices. We illustrate this in the rank two case.

An explicit solution to the weak Schottky problem

We give an explicit weak solution to the Schottky problem, in the spirit of Riemann and Schottky. For any genus $g$, we write down a collection of polynomials in genus $g$ theta constants, such that their common zero locus contains the locus of Jacobians of genus $g$ curves as an irreducible component. These polynomials arise by applying a specific Schottky-Jung proportionality to an explicit collection of quartic identities for theta constants in genus $g-1$, which are suitable linear combinations of Riemann's quartic relations.

θ乘积与椭圆积分矩的周期关系

Period Relations for Theta Products and Elliptic Integral Moments

该研究开发周期多项式方法，解释完全椭圆积分矩间已知有理关系，为模形式临界L-值的相关关系提供概念性说明。

由Jacobi theta函数与特殊对称多项式产生的拟模形式

Quasimodular forms arising from Jacobi's theta function and special symmetric polynomials

本文利用Ramanujan的拟模形式序列构造出Γ_0(4)上的权n拟模形式，其对称函数化身给出对称多项式T_n，从而解决关于T_n的两个猜想，并揭示其与旋量流形Borel-Hirzebruch Â-亏格的联系。

局部theta对应与Galois周期

Local theta correspondence and Galois periods

本文研究了局部theta对应下偶正交群和辛群Galois周期的性质，比较了乘数并建立了共轭与相对特征关系。

Algebraic independence results for values of Jacobi theta-constants

Let $θ_3(τ)=1+2\sum_{ν=1}^{\infty} q^{ν^2}$ with $q=e^{iπτ}$ and $\Im (τ)>0$ denote the Thetanullwert of the Jacobi theta function \[θ(z|τ) \,=\,\sum_{ν=-\infty}^{\infty} e^{πiν^2τ+ 2πiνz} \,.\] Moreover, let $θ_2(τ)=2\sum_{ν=0}^{\infty} q^{{(ν+1/2)}^2}$ and $θ_4(τ)=1+2\sum_{ν=1}^{\infty} {(-1)}^νq^{ν^2}$. For every even integer $n\geq 6$, which is not a power of two, we prove constructively the existence of a nontrivial integer polynomial $Q_n(X,Y)$ such that \[Q_n\Big( \,\frac{θ_3^4(nτ)}{θ_3^4(τ)},\frac{θ_2^4(τ)}{θ_3^4(τ)}\, \Big) \,=\, 0 \] holds for all complex numbers $τ$ from the upper h…

树状链环与模尾

Arborescent links and modular tails

本文针对树状链环证明了着色琼斯多项式尾部的显式公式，以 theta 函数乘积表示，并为交错纽结的模性分类提供数值证据。

On the theta operator for modular forms modulo prime powers

We consider the classical theta operator $θ$ on modular forms modulo $p^m$ and level $N$ prime to $p$ where $p$ is a prime greater than 3. Our main result is that $θ$ mod $p^m$ will map forms of weight $k$ to forms of weight $k+2+2p^{m-1}(p-1)$ and that this weight is optimal in certain cases when $m$ is at least 2. Thus, the natural expectation that $θ$ mod $p^m$ should map to weight $k+2+p^{m-1}(p-1)$ is shown to be false. The primary motivation for this study is that application of the $θ$ operator on eigenforms mod $p^m$ corresponds to twisting the attached Galois representations with the …

与自对偶晶格相关的θ函数零点

Zeros of theta functions associated with self-dual lattices

研究自对偶晶格相关θ函数零点的分布特性，揭示偶晶格和奇晶格中零点的不同行为。

Weighted Generating Functions for Type II Lattices and Codes

We give a new structural development of harmonic polynomials on Hamming space, and harmonic weight enumerators of binary linear codes, that parallels one approach to harmonic polynomials on Euclidean space and weighted theta functions of Euclidean lattices. Namely, we use the finite-dimensional representation theory of sl_2 to derive a decomposition theorem for the spaces of discrete homogeneous polynomials in terms of the spaces of discrete harmonic polynomials, and prove a generalized MacWilliams identity for harmonic weight enumerators. We then present several applications of harmonic weigh…

Discriminants of Chebyshev Radical Extensions

Let t be any integer and fix an odd prime ell. Let Phi(x) = T_ell^n(x)-t denote the n-fold composition of the Chebyshev polynomial of degree ell shifted by t. If this polynomial is irreducible, let K = bbq(theta), where theta is a root of Phi. A theorem of Dedekind's gives a condition on t for which K is monogenic. For other values of t, we apply the Montes algorithm to obtain a formula for the discriminant of K and to compute basis elements for the ring of integers O_K.

Riemann $\xi$ 函数的模表示及等价于 Riemann 假设的多项式不等式

Modulus representation of the Riemann $ξ$ function and polynomial inequalities equivalent to the Riemann hypothesis

本文利用 Jacobi theta 函数给出 Riemann ξ 函数的模表示，并证明 Riemann 假设等价于一族多项式不等式，同时给出初步结果。