English

On the Stanley depth of powers of edge ideals

Commutative Algebra 2015-09-17 v1 Combinatorics

Abstract

Let K\mathbb{K} be a field and S=K[x1,,xn]S=\mathbb{K}[x_1,\dots,x_n] be the polynomial ring in nn variables over K\mathbb{K}. Let GG be a graph with nn vertices. Assume that I=I(G)I=I(G) is the edge ideal of GG and pp is the number of its bipartite connected components. We prove that for every positive integer kk, the inequalities sdepth(Ik/Ik+1)p{\rm sdepth}(I^k/I^{k+1})\geq p and sdepth(S/Ik)p{\rm sdepth}(S/I^k)\geq p hold. As a consequence, we conclude that S/IkS/I^k satisfies the Stanley's inequality for every integer kn1k\geq n-1. Also, it follows that Ik/Ik+1I^k/I^{k+1} satisfies the Stanley's inequality for every integer k0k\gg 0. Furthermore, we prove that if (i) GG is a non-bipartite graph, or (ii) at least one of the connected components of GG is a tree with at least one edge, then IkI^k satisfies the Stanley's inequality for every integer kn1k\geq n-1. Moreover, we verify a conjecture of the author in special cases.

Keywords

Cite

@article{arxiv.1509.04988,
  title  = {On the Stanley depth of powers of edge ideals},
  author = {S. A. Seyed Fakhari},
  journal= {arXiv preprint arXiv:1509.04988},
  year   = {2015}
}