English

Integral Chow rings of modular compactifications of $\mathcal{M}_{1,n\leq 6}$

Algebraic Geometry 2026-04-08 v2

Abstract

For n6n\leq 6, we compute the integral Chow ring of every modular compactification of M1,n\mathcal{M}_{1,n} parametrising only Gorenstein curves with smooth, distinct markings. These include the Deligne--Mumford, Schubert, and Smyth compactifications, and many more. They can all be excised from the stack of log-canonically polarised Gorenstein curves. The Chow ring of the latter admits a simple, combinatorial description, which we compute by patching along a natural stratification by core level. We further deduce that all these modular compactifications satisfy the Chow-K\"{u}nneth generation property, that the cycle class map is an isomorphism, and for n=4n=4 we study whether the Getzler's relation hold integrally.

Keywords

Cite

@article{arxiv.2505.04587,
  title  = {Integral Chow rings of modular compactifications of $\mathcal{M}_{1,n\leq 6}$},
  author = {Luca Battistella and Andrea Di Lorenzo},
  journal= {arXiv preprint arXiv:2505.04587},
  year   = {2026}
}

Comments

v2: final version, to appear on Crelle