English

Derived functors and Hilbert polynomials over hypersurface rings-II

Commutative Algebra 2025-07-01 v1

Abstract

Let (A,m)(A,\mathfrak{m}) be a hypersurface local ring of dimension d1d \geq 1, NN a perfect AA-module and let II be an ideal in AA with (N/IN)\ell(N/IN) finite. We show that there is a integer rI1r_I \geq -1 (depending only on II and NN) such that if MM is any non-free maximal \CM \ (= MCM) AA-module the functions n(Tor1A(M,N/In+1N))n \rightarrow \ell(\text{Tor}^A_1(M, N/I^{n+1}N)), n(ExtA1(M,N/In+1N))n \rightarrow \ell(\text{Ext}^1_A(M, N/I^{n+1}N)) and n(Extd+1(N/In+1N,M))n \rightarrow \ell(\text{Ext}^{d+1}(N/I^{n+1}N, M)) (which are all of polynomial type) has degree rIr_I. Surprisingly a key ingredient is the classification of thick subcategories of the stable category of MCM AA-modules (obtained by Takahashi, see \cite[6.6]{T}).

Keywords

Cite

@article{arxiv.2506.23241,
  title  = {Derived functors and Hilbert polynomials over hypersurface rings-II},
  author = {Tony J. Puthenpurakal},
  journal= {arXiv preprint arXiv:2506.23241},
  year   = {2025}
}

Comments

This is part two of our earlier paper arXiv:2404.14938

R2 v1 2026-07-01T03:38:29.694Z