English

A Hyperbolic Analogue of the Rademacher Symbol

Number Theory 2025-04-01 v4

Abstract

One of the most famous results of Dedekind is the transformation law of logΔ(z)\log \Delta(z). After a half-century, Rademacher modified Dedekind's result and introduced an SL2(Z)\mathrm{SL}_2(\mathbb{Z})-conjugacy class invariant (integer-valued) function Ψ(γ)\Psi(\gamma) called the Rademacher symbol. Inspired by Ghys' work on modular knots, Duke-Imamo\={g}lu-T\'{o}th (2017) constructed a hyperbolic analogue of the symbol. In this article, we study their hyperbolic analogue of the Rademacher symbol Ψγ(σ)\Psi_\gamma(\sigma) and provide its two types of explicit formulas by comparing it with the classical Rademacher symbol. In association with it, we contrastively show Kronecker limit type formulas of the parabolic, elliptic, and hyperbolic Eisenstein series. These limits give harmonic, polar harmonic, and locally harmonic Maass forms of weight 2.

Keywords

Cite

@article{arxiv.2003.12354,
  title  = {A Hyperbolic Analogue of the Rademacher Symbol},
  author = {Toshiki Matsusaka},
  journal= {arXiv preprint arXiv:2003.12354},
  year   = {2025}
}

Comments

38 pages. This article is published in Mathematische Annalen. It differs from v3 with the addition of a new Appendix B. Furthermore, while Appendix C has been removed in the published version, it remains unchanged in this preprint