A second-quantized version of Mathieu moonshine leads to product formulae for functions that are potentially genus-two Siegel Modular Forms analogous the Igusa Cusp Form. The modularity these do not follow in an obvious manner. For some conjugacy classes, but all, they match known modular forms. In this paper, we express all classes $M_{24}$ terms products standard This provides a new proof the...

It is proved that the ring of Siegel modular forms in any genus is determined by doubly-even self-dual codes and the theta relations. The (higher) weight polynomials of such codes are proved to be the generators of the ring of invariants of a polynomial ring in 2 g variables under a certain speciied nite group. Moreover codes are uniquely determined by their weight polynomials.

We investigate Poincaré series, where we average products of terms of Fourier series of real-analytic Siegel modular forms. There are some (trivial) special cases for which the products of terms of Fourier series of elliptic modular forms and harmonic Maass forms are almost holomorphic, in which case the corresponding Poincaré series are almost holomorphic as well. In general, this is not the c...

This paper explicitly describes the procedure of associating an automorphic representation of PGSp(2n, A) with a Siegel modular form of degree n for the full modular group Γn = Sp(2n, Z), generalizing the well-known procedure for n = 1. This will show that the so-called “standard” and “spin” L-functions associated with such forms are obtained as Langlands L-functions. The theory of Euler produc...

The moduli space of principally polarized abelian surfaces is parametrized by three Igusa functions. In this article we investigate a new way to evaluate these functions by using Siegel Eisenstein series. We explain how to compute the Fourier coefficients of certain Siegel modular forms using classical modular forms of halfintegral weight. One of the results in this paper is an explicit algorit...