Affine Semigroups of Maximal Projective Dimension

A submonoid of Nd is of maximal projective dimension (MPD) if the associated affine semigroup k-algebra has the maximum possible projective dimension. Such submonoids have a nontrivial set of pseudo-Frobenius elements. We generalize the notion of symmetric semigroups, pseudo-symmetric semigroups, and row-factorization matrices for pseudo-Frobenius elements of numerical semigroups to the case of MPDsemigroups in Nd. We prove that under suitable conditions these semigroups satisfy the generalizedWilf’s conjecture. We prove that the generic nature of the defining ideal of the associated semigroup algebra of an MPD-semigroup implies the uniqueness of the row-factorization matrix for each pseudo-Frobenius element. Further, we give a description of pseudo-Frobenius elements and row-factorization matrices of gluing of MPD-semigroups. We prove that the defining ideal of gluing of MPD-semigroups is never generic.