English

Distributive properties of division points and discriminants of Drinfeld modules

Number Theory 2024-02-02 v1

Abstract

We present a new notion of distribution and derived distribution of rank rNr \in \mathbb{N} for a global function field KK with a distinguished place \infty. It allows to describe the relations between division points, isogenies, and discriminants both for a fixed Drinfeld module of rank rr for the above data, or for the corresponding modular forms. We introduce and study three basic distributions with values in Q\mathbb{Q}, in the group μ(K)\mu(\overline{K}) of roots of unity in the algebraic closure K\overline{K} of KK, and in the group U(1)(C)U^{(1)}(C_{\infty}) of 11-units of the completed algebraic closure CC_{\infty} of KK_{\infty}, respectively. There result product formulas for division points and discriminants that encompass known results (e.g. analogues of Wallis' formula for (2πi)2(2\pi i)^{2} in the rank-11 case, of Jacobi's formula Δ=(2πi)12q(1qn)24\Delta = (2\pi i)^{12} q \prod (1-q^{n})^{24} in the rank-22 case, and similar boundary expansions for r>2r > 2) and several new ones: the definition of a canonical discriminant for the most general case of Drinfeld modules and the description of the sizes of division and discriminant forms. In the now classical case where (K,)=(Fq(T),)(K, \infty) = (\mathbb{F}_{q}(T), \infty) and r=1r = 1, 22 or 33, we give explicit values for the logarithms of such forms.

Keywords

Cite

@article{arxiv.2402.00545,
  title  = {Distributive properties of division points and discriminants of Drinfeld modules},
  author = {Ernst-Ulrich Gekeler},
  journal= {arXiv preprint arXiv:2402.00545},
  year   = {2024}
}

Comments

32 pages, comments welcome