English

Growth of Hilbert coefficients of Syzygy modules

Commutative Algebra 2015-01-30 v1

Abstract

Let (A,m)(A,\mathfrak{m}) be a complete intersection ring of dimension dd and let II be an m\mathfrak{m}-primary ideal. Let MM be a maximal \CM \ AA-module. For i=0,1,,di = 0,1,\cdots,d, let eiI(M)e_i^I(M) denote the ithi^{th} Hilbert -coefficient of MM with respect to II. We prove that for i=0,1,2i = 0, 1, 2, the function jeiI(SyzjA(M))j \mapsto e_i^I(Syz_j^A(M)) is of quasi-polynomial type with period 22. Let GI(M)G_I(M) be the associated graded module of MM with respect to II. If GI(A)G_I(A) is Cohen-Macaulay and dimA2\dim A \leq 2 we also prove that the functions jdepth GI(Syz2j+iA(M))j \mapsto depth \ G_I(Syz^A_{2j+i}(M)) are eventually constant for i=0,1i = 0, 1. Let ξI(M)=limldepth GIl(M)\xi_I(M) = \lim_{l \rightarrow \infty} depth \ G_{I^l}(M). Finally we prove that if dimA=2\dim A = 2 and GI(A)G_I(A) is Cohen-Macaulay then the functions jξI(Syz2j+iA(M))j \mapsto \xi_I(Syz^A_{2j + i}(M)) are eventually constant for i=0,1i = 0, 1.

Keywords

Cite

@article{arxiv.1501.07403,
  title  = {Growth of Hilbert coefficients of Syzygy modules},
  author = {Tony J. Puthenpurakal},
  journal= {arXiv preprint arXiv:1501.07403},
  year   = {2015}
}