Winding quotients for virtual period maps of rank 1
Kyoji Saito
TL;DR
The paper develops a rank-1 model of virtual period maps that exhibits a winding phenomenon, producing a winding quotient $E_{\tau}$ that reframes the inversion problem for period maps. It introduces $q$-multiplicatively periodic objects $\mathcal{U},\mathcal{V},\mathcal{W}$ on the winding quotient, whose pull-backs recover the Weierstrass data up to Eisenstein corrections, linking to Borcherds' expansions. The main result provides an explicit morphism from the winding quotient $\mathbb{C}_w^\times$ to the elliptic curve $E_{\tau}$ in terms of $\mathcal{W}$ and its derivative, thereby solving the new inversion problem in this non-geometric setting. The work connects classical elliptic function theory with $q$-shifted factorial frameworks and suggests intriguing links to mathematical physics via propagator-type constructions on elliptic curves.
Abstract
We illustrate a rank 1 model of virtual period maps and their associated winding quotient, where the winding quotient is a new phenomenon appeared in a recent study of virtual period maps and it requires a reformulation of the classical Jacobi inversion problem for the period maps. We answer to the new inversion problem by introducing the q-multiplicatively periodic function, whose pull-back to the winding covering space is the Weierstrass p-function up to a correction by Eisenstein series E2. The function appears also in the study of mathematical physics as the propagator on elliptic curves.
