Seminario - Almost symmetric numerical semigroups

Il giorno 31 agosto, alle ore 11, in aula da definirsi, il prof. K Watanabe (Nihon University) terrà un seminario dal titolo "Almost symmetric numerical semigroups".

Joint work with J. Herzog. We study almost symmetric numerical semigroups and semigroup rings. We describe a characteristic property
of the minimal free resolution of the semigroup ring of an almost
symmetric numerical semigroup. For almost symmetric semigroups generated
by 4 elements we will give a structure theorem by using the ?row-factorization matrices?, introduced by Moscariello.
As a result, we give a simpler proof of Komeda?s structure theorem
of pseudo-symmetric numerical semigroups generated by 4 elements.

Row-factorization matrices are also used to study shifted families of numerical semigroups.