turkmath.org

Let a1, . . . , a4 be positive integers with gcd(a1, . . . , a4) = 1, and S =< a1, . . . , a4 > be the numerical semigroup generated by a1, . . . , a4. In this talk we determine a minimal binomial generating set for the toric ideal associated to S. Our approach is based on the detection of those binomials and monomials that have to appear in every system of binomial generators of the toric ideal; these special binomials and monomials are called indispensable in the literature.