Graphs of Hecke operators in mixed ramification

Fuente: arXiv
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Main Authors: Kashyap, Rudrendra, Zveryk, Vladyslav
Format: Preprint
Published: 2026
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author Kashyap, Rudrendra
Zveryk, Vladyslav
author_facet Kashyap, Rudrendra
Zveryk, Vladyslav
contents We study Hecke operators on moduli spaces of ramified $G$-bundles using the combinatorial language of Hecke graphs. We introduce a general notion of $\mathcal H$-ramification in the spirit of parahoric ramification, which depends on a choice of a divisor and subgroups of $G$ at every point of the divisor. Building on our previous work, we prove that, under mild regularity conditions, the action of a Hecke operator in the deep cusp of $\mathrm{Bun}_G$ in a highly complex ramification mimics an action in a much simpler ramification. This reduces the study to a smaller number of cases which, in particular, involve divisors supported at no more than two points. We demonstrate our methods by computing various examples for $G=\mathrm{PGL}_2$ and computing the dimensions of spaces of Hecke eigenforms for generic eigenvalues.
format Preprint
id arxiv_https___arxiv_org_abs_2605_13824
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Graphs of Hecke operators in mixed ramification
Kashyap, Rudrendra
Zveryk, Vladyslav
Algebraic Geometry
Number Theory
Representation Theory
We study Hecke operators on moduli spaces of ramified $G$-bundles using the combinatorial language of Hecke graphs. We introduce a general notion of $\mathcal H$-ramification in the spirit of parahoric ramification, which depends on a choice of a divisor and subgroups of $G$ at every point of the divisor. Building on our previous work, we prove that, under mild regularity conditions, the action of a Hecke operator in the deep cusp of $\mathrm{Bun}_G$ in a highly complex ramification mimics an action in a much simpler ramification. This reduces the study to a smaller number of cases which, in particular, involve divisors supported at no more than two points. We demonstrate our methods by computing various examples for $G=\mathrm{PGL}_2$ and computing the dimensions of spaces of Hecke eigenforms for generic eigenvalues.
title Graphs of Hecke operators in mixed ramification
topic Algebraic Geometry
Number Theory
Representation Theory
url https://arxiv.org/abs/2605.13824