English

On the algebraic invariants of certain affine semigroup algebras

Commutative Algebra 2022-07-07 v1

Abstract

Let aa and dd be two linearly independent vectors in N2\mathbb{N}^2, over the field of rational numbers. For a positive integer k2k \geq 2, consider the sequence a,a+d,,a+kda, a+d, \ldots, a+kd such that the affine semigroup Sa,d,k=a,a+d,,a+kdS_{a,d,k} = \langle a, a+d, \ldots, a+kd \rangle is minimally generated by this sequence. We study the properties of affine semigroup algebra k[Sa,d,k]k[S_{a,d,k}] associated to this semigroup. We prove that k[Sa,d,k]k[S_{a,d,k}] is always Cohen-Macaulay and it is Gorenstein if and only if k=2k=2. For k=2,3,4k=2,3,4, we explicitly compute the syzygies, minimal graded free resolution and Hilbert series of k[Sa,d,k].k[S_{a,d,k}]. We also give a minimal generating set and a Gr\"{o}bner basis of the defining ideal of k[Sa,d,k].k[S_{a,d,k}]. Consequently, we prove that k[Sa,d,k]k[S_{a,d,k}] is Koszul. Finally, we prove that the Castelnuovo-Mumford regularity of k[Sa,d,k]k[S_{a,d,k}] is 11 for any a,d,k.a,d,k.

Keywords

Cite

@article{arxiv.2207.02675,
  title  = {On the algebraic invariants of certain affine semigroup algebras},
  author = {Om Prakash Bhardwaj and Indranath Sengupta},
  journal= {arXiv preprint arXiv:2207.02675},
  year   = {2022}
}