Representation stability for moduli spaces of admissible covers

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Hauptverfasser: Chang-Lee, Megan, Kannan, Siddarth, Tosteson, Philip
Format: Preprint
Veröffentlicht: 2025
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author Chang-Lee, Megan
Kannan, Siddarth
Tosteson, Philip
author_facet Chang-Lee, Megan
Kannan, Siddarth
Tosteson, Philip
contents We prove a representation stability result for the sequence of spaces $\overline M_{g, n}^A$ of pointed admissible $A$-covers of stable $n$-pointed genus-$g$ curves, for an abelian group $A$. For fixed genus $g$ and homology degree $i$, we give the sequence of rational homology groups $H_i(\overline{M}_{g, n}^A;\mathbb Q)$ the structure of a module over a combinatorial category, a la Sam--Snowden, and prove that this module is generated in degree at most $g + 5 i$. This implies that the generating function for the ranks of the homology groups is rational, with poles in the set $\left\{-1, -\frac{1}{2}, \ldots, -\frac{1}{|A|^2\cdot(g + 5i)}\right\}$. In the case where $A$ is the trivial group, our work significantly improves on previous representation stability results on the Deligne--Mumford compactification $\overline M_{g, n}$.
format Preprint
id arxiv_https___arxiv_org_abs_2506_22640
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Representation stability for moduli spaces of admissible covers
Chang-Lee, Megan
Kannan, Siddarth
Tosteson, Philip
Algebraic Geometry
Geometric Topology
14H10, 16G20
We prove a representation stability result for the sequence of spaces $\overline M_{g, n}^A$ of pointed admissible $A$-covers of stable $n$-pointed genus-$g$ curves, for an abelian group $A$. For fixed genus $g$ and homology degree $i$, we give the sequence of rational homology groups $H_i(\overline{M}_{g, n}^A;\mathbb Q)$ the structure of a module over a combinatorial category, a la Sam--Snowden, and prove that this module is generated in degree at most $g + 5 i$. This implies that the generating function for the ranks of the homology groups is rational, with poles in the set $\left\{-1, -\frac{1}{2}, \ldots, -\frac{1}{|A|^2\cdot(g + 5i)}\right\}$. In the case where $A$ is the trivial group, our work significantly improves on previous representation stability results on the Deligne--Mumford compactification $\overline M_{g, n}$.
title Representation stability for moduli spaces of admissible covers
topic Algebraic Geometry
Geometric Topology
14H10, 16G20
url https://arxiv.org/abs/2506.22640