English

Free resolutions and marked families

Commutative Algebra 2025-10-31 v1 Algebraic Geometry

Abstract

Let K\mathbb{K} be a field and AA a Noetherian K\mathbb{K}-algebra. In a paper of 2020, M. Albert, C. Bertone, M. Roggero and W. M. Seiler proved that, given a quasi-stable module URmU \subset R^m with R=K[x0,,xn]R=\mathbb{K}[x_0,\dots,x_n], any submodule M(RA)mM\subseteq (R\otimes A)^m generated by a marked basis over UU admits a special free resolution described in terms of marked bases as well, called the {\em UU-resolution of MM}. In this paper, we first investigate the minimality of the UU-resolution and its structure. When MM is an ideal and A=KA=\mathbb{K}, we show that MM is componentwise linear if and only if its UU-resolution is minimal, up to a linear change of variables. Then, adopting a functorial approach to the construction of the UU-resolution, we prove that certain functors naturally associated with the resolution are isomorphic. These isomorphisms arise from the fact that the marked basis of the ii-th syzygy module in the UU-resolution can be expressed in terms of the coefficients of the marked basis of MM. Moreover, when MM is an ideal of depth at least 2, this correspondence can be reversed: in this case, the marked basis of MM itself can be written in terms of the coefficients of the marked basis of its first syzygy module.

Keywords

Cite

@article{arxiv.2510.26409,
  title  = {Free resolutions and marked families},
  author = {Cristina Bertone and Francesca Cioffi and Paolo Lella},
  journal= {arXiv preprint arXiv:2510.26409},
  year   = {2025}
}

Comments

28 pages, 7 Macaulay2 ancillary files, comments welcome