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    Dilatations of numerical semigroups

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    This paper is focused on numerical semigroups and presents a simple construction, that we call “dilatation”, which, from a starting semigroup S, permits to get an infinite family of semigroups which share several properties with S. The invariants of each semigroup T of this family are given in terms of the corresponding invariants of S and both the Apéry set and the minimal generators of T are described. We also study three properties that are close to the Gorenstein property of the associated semigroup ring: almost Gorenstein, 2-AGL, and nearly Gorenstein properties. More precisely, we prove that S satisfies one of these properties if and only if each dilatation of S satisfies the corresponding one

    Families of Gorenstein and almost Gorenstein rings

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    Starting with a commutative ring R and an ideal I, it is possible to define a family of rings R(I)_{a,b}, with a, b∈R, as quotients of the Rees algebra ⊕_{n≥0} I^n t^n; among the rings appearing in this family we find Nagata’s idealization and amalgamated duplication. Many properties of these rings depend only on R and I and not on a, b; in this paper we show that the Gorenstein and the almost Gorenstein properties are independent of a, b. More precisely, we characterize when the rings in the family are Gorenstein, complete intersection, or almost Gorenstein and we find a formula for the type

    Dilatations of numerical semigroups

    No full text
    This paper is focused on numerical semigroups and presents a simple construction, that we call "dilatation", which, from a starting semigroup S, permits to get an infinite family of semigroups which share several properties with S. The invariants of each semigroup T of this family are given in terms of the corresponding invariants of S and both the Apéry set and the minimal generators of T are described. We also study three properties that are close to the Gorenstein property of the associated semigroup ring: almost Gorenstein, 2-AGL, and nearly Gorenstein properties. More precisely, we prove that S satisfies one of these properties if and only if each dilatation of S satisfies the corresponding one

    A family of quotients of the Rees Algebra

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    A family of quotient rings of the Rees algebra associated to a com- mutative ring is studied. This family generalizes both the classical concept of idealization by Nagata and a more recent concept, the amalgamated duplication of a ring. It is shown that several properties of the rings of this family do not depend on the particular member
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