English

Numerical semigroups via projections and via quotients

Commutative Algebra 2024-04-16 v3 Combinatorics

Abstract

We examine two natural operations to create numerical semigroups. We say that a numerical semigroup S\mathcal{S} is kk-normalescent if it is the projection of the set of integer points in a kk-dimensional polyhedral cone, and we say that S\mathcal{S} is a kk-quotient if it is the quotient of a numerical semigroup with kk generators. We prove that all kk-quotients are kk-normalescent, and although the converse is false in general, we prove that the projection of the set of integer points in a cone with kk extreme rays (possibly lying in a dimension smaller than kk) is a kk-quotient. The discrete geometric perspective of studying cones is useful for studying kk-quotients: in particular, we use it to prove that the sum of a k1k_1-quotient and a k2k_2-quotient is a (k1+k2)(k_1+k_2)-quotient. In addition, we prove several results about when a numerical semigroup is not kk-normalescent.

Keywords

Cite

@article{arxiv.2306.11564,
  title  = {Numerical semigroups via projections and via quotients},
  author = {Tristram Bogart and Christopher O'Neill and Kevin Woods},
  journal= {arXiv preprint arXiv:2306.11564},
  year   = {2024}
}
R2 v1 2026-06-28T11:09:42.269Z