English

Nonincreasing depth functions of monomial ideals

Commutative Algebra 2016-12-02 v3

Abstract

Given a nonincreasing function f:Z0{0}Z0f : \mathbb{Z}_{\geq 0} \setminus \{ 0 \} \to \mathbb{Z}_{\geq 0} such that (i) f(k)f(k+1)1f(k) - f(k+1) \leq 1 for all k1k \geq 1 and (ii) if a=f(1)a = f(1) and b=limkf(k)b = \lim_{k \to \infty} f(k), then f1(a)f1(a1)f1(b+1)|f^{-1}(a)| \leq |f^{-1}(a-1)| \leq \cdots \leq |f^{-1}(b+1)|, a system of generators of a monomial ideal IK[x1,,xn]I \subset K[x_1, \ldots, x_n] for which depthS/Ik=f(k){\rm depth} S/I^k = f(k) for all k1k \geq 1 is explicitly described. Furthermore, we give a characterization of triplets of integers (n,d,r)(n,d,r) with n>0n > 0, d0d \geq 0 and r>0r > 0 with the properties that there exists a monomial ideal IS=K[x1,,xn]I \subset S = K[x_1, \ldots, x_n] for which limkdepthS/Ik=d\lim_{k \to \infty} {\rm depth} S/I^k = d and dstab(I)=r{\rm dstab}(I) = r, where dstab(I){\rm dstab}(I) is the smallest integer k01k_0 \geq 1 with depthS/Ik0=depthS/Ik0+1=depthS/Ik0+2={\rm depth} S/I^{k_0} = {\rm depth} S/I^{k_0+1} = {\rm depth} S/I^{k_0+2} = \cdots.

Keywords

Cite

@article{arxiv.1607.07223,
  title  = {Nonincreasing depth functions of monomial ideals},
  author = {Kazunori Matsuda and Tao Suzuki and Akiyoshi Tsuchiya},
  journal= {arXiv preprint arXiv:1607.07223},
  year   = {2016}
}

Comments

7 pages

R2 v1 2026-06-22T15:03:20.185Z