A note on strong affine semigroups

Abstract

This work introduces and studies strong affine semigroups, extending the notion of strong numerical semigroups to the higher-dimensional setting. We show that non-numerical strong affine semigroups present structural differences with respect to strong numerical semigroups. Special attention is devoted to strong $\mathcal C$-semigroups. We prove that the family of strong $\mathcal C$-semigroups with a given set of multiplicities $E$ admits a maximal element and has a tree structure. We characterize when this family is finite and provide an algorithm to compute all such semigroups up to a fixed genus. We also introduce the notion of special strong affine semigroups and obtain refined versions of several previous results. Finally, we study toric ideals arising from strong affine semigroups, determining their indispensable monomials and Betti elements for several families.