An explicit upper bound for the HSL number of the top local cohomology module of affine semigroup rings

Abstract

The Hartshorne-Speiser-Lyubeznik number is a numerical invariant that can often be used to bound the Frobenius test exponent of positive characteristic rings. In this paper we look at positive characteristic semigroup rings generated by affine torsion-free abelian cancellative pointed semigroups that contain an identity, and compute an upper bound for the Hartshorne-Speiser-Lyubeznik number of their top local cohomology module at the maximal monomial ideal.