English

The fiber-full scheme

Algebraic Geometry 2025-07-08 v3 Commutative Algebra

Abstract

We introduce the fiber-full scheme which can be seen as the parameter space that generalizes the Hilbert and Quot schemes by controlling the entire cohomological data. The fiber-full scheme FibF/X/Sh\text{Fib}_{\mathcal{F}/X/S}^\mathbf{h} is a fine moduli space parametrizing all quotients G\mathcal{G} of a fixed coherent sheaf F\mathcal{F} on a projective morphism f:XPSrSf:X \subset \mathbb{P}_S^r \rightarrow S such that Rif(G(ν))R^i{{f}_*}\left(\mathcal{G}(\nu)\right) is a locally free OS\mathcal{O}_S-module of rank equal to hi(ν)h_i(\nu), where h=(h0,,hr):Zr+1Nr+1\mathbf{h} = (h_0,\ldots,h_r) : \mathbb{Z}^{r+1} \rightarrow \mathbb{N}^{r+1} is a fixed tuple of functions. In other words, the fiber-full scheme controls the dimension of all cohomologies of all possible twistings, instead of just the Hilbert polynomial. We show that the fiber-full scheme is a quasi-projective SS-scheme and a locally closed subscheme of its corresponding Quot scheme. In the context of applications, we demonstrate that the fiber-full scheme provides the natural parameter space for arithmetically Cohen-Macaulay and arithmetically Gorenstein schemes with fixed cohomological data, and for square-free Gr\"obner degenerations.

Keywords

Cite

@article{arxiv.2108.13986,
  title  = {The fiber-full scheme},
  author = {Yairon Cid-Ruiz and Ritvik Ramkumar},
  journal= {arXiv preprint arXiv:2108.13986},
  year   = {2025}
}

Comments

To appear in Journal of Pure and Applied Algebra

R2 v1 2026-06-24T05:34:22.603Z