On the Bernoulli--Hurwitz periods
Luochen Zhao
TL;DR
This work develops a comprehensive $p$-adic framework for Bernoulli--Hurwitz numbers attached to CM elliptic curves with a split prime, constructing a $p$-adic measure $\mu_{\mathrm{BH}}$ from elliptic functions and proving that its periods are special values of a weight-one Eisenstein family. By connecting these periods to Katz’s $p$-adic Eisenstein measure, the authors obtain explicit interpolation formulas for the Bernoulli--Hurwitz $p$-adic zeta function $\zeta_p^{\mathrm{BH}}(s)$ across ordinary CM and non-CM elliptic curves, including a $p$-adic first limit formula. The strategy hinges on modularity of $q$-expansions and the appearance of weight-one Hasse-type invariants, enabling congruence-based propagation of period relations to special values while avoiding elliptic units. The results illuminate the interpolation behavior of $p$-adic zeta functions in the CM setting and suggest new connections to Gross-type factorizations and CM Chowla–Selberg-type formulas, with potential extensions to broader CM contexts via Katz’s Eisenstein machinery. Overall, the paper provides a modularity-driven, arithmetic interpolation framework for Bernoulli--Hurwitz measures and their $p$-adic zeta functions for ordinary elliptic curves.
Abstract
Let $E$ be an elliptic curve having CM by the ring of integers of an imaginary quadratic field $K$ in which $p$ splits. Following Lichtenbaum, the Bernoulli--Hurwitz numbers of $E$ (i.e., values of Eisenstein series evaluated at $E$ up to normalization) admit integral representations given by a $p$-adic measure constructed from an elliptic function. We show that the periods of this measure are in fact special values of a family of weight one Eisenstein series at the CM curve $E$ equipped with certain level data, and explicitly relate it to Katz's one-variable $p$-adic Eisenstein measure, whereby we derive period formulas of the Bernoulli--Hurwitz measure attached to any ordinary elliptic curve $\mathcal{E}$ defined over a local field. Moreover, by exploiting the modularity of these periods, and thanks to the existence of abundant weight one Hasse-type invariants, we present a novel approach to the interpolation property of the Bernoulli--Hurwitz $p$-adic zeta functions of the ordinary elliptic curve $\mathcal{E}$, and obtain a $p$-adic Kronecker's first limit formula.
