A note on Artin Gorenstein algebras with Hilbert function (1,4,k,k,4,1)

Abstract

We study the free resolutions of some Artin Gorenstein algebras of Hilbert function $(1,4,k,k,4,1)$ and we prove that all such algebras have the Strong Lefschetz property if they have the Weak Lefschetz property. In the case $k=4$ we prove that the Hilbert function alone fixes the betti table. For higher $k$ stronger conditions on the algebras are needed to fix the betti table. In particular, if the algebra is a complete intersection or if it is defined by an equigenerated ideal then the betti table is unique.