Forum of Mathematics, Sigma (Jan 2024)
Eichler–Selberg relations for singular moduli
Abstract
The Eichler–Selberg trace formula expresses the trace of Hecke operators on spaces of cusp forms as weighted sums of Hurwitz–Kronecker class numbers. We extend this formula to a natural class of relations for traces of singular moduli, where one views class numbers as traces of the constant function $j_0(\tau )=1$ . More generally, we consider the singular moduli for the Hecke system of modular functions
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