Partition of the complement of good semigroup ideals and Apéry sets

Good semigroups form a class of submonoids of Nd containing the value semigroups of curve singularities. In this article, we describe a partition of the complement of good semigroup ideals. As main application, we describe the Apéry sets of good semigroups with respect to arbitrary elements. This generalizes to any d≥2 the results in the study of D’Anna et al., which are proved in the case d = 2 and only for the standard Apéry set with respect to the smallest nonzero element. Several new results describing good semigroups in Nd are also provided.