On the diagonal subalgebra of an Ext algebra

Edward L. Green, Nicole Snashall, Øyvind Solberg +1

Let $R$ be a Koszul algebra over a field $k$ and $M$ be a linear $R$-module. We study a graded subalgebra ${\Delta }_M$ of the Ext-algebra ${\mathrm{Ext}}_R^{\ast }(M,M)$ called the diagonal…