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Acta Mathematica Vietnamica

Betti Numbers of the Tangent Cones of Monomial Space Curves

Nguyen P. H. Lan , Nguyen Chanh Tu , icon-email Thanh Vu

Abstract

Let H=n1,n2,n3 be a numerical semigroup. Let H~ be the interval completion of H, namely the semigroup generated by the interval n1,n1+1,,n3. Let K be a field and K[H] the semigroup ring generated by H. Let IH be the defining ideal of the tangent cone of K[H]. In this paper, we describe the defining equations of IH. From that, we prove the Herzog-Stamate conjecture for monomial space curves stating that βi(IH)βi(IH~) for all i, where βi(IH) and βi(IH~) are the ith Betti numbers of IH and IH~ respectively.