Subalgebras of bigraded Koszul algebras

摘要

We show that diagonal subalgebras and generalized Veronese subrings of a bigraded Koszul algebra are Koszul. We give upper bounds for the regularity of side-diagonal and relative Veronese modules and apply the results to symmetric algebras and Rees rings. (C) 2001 Academic Press. [References: 15]