4 papers · 1 filter
Independence of the total reflexivity conditions for modules
David Jorgensen, Liana Sega
We show that the conditions defining total reflexivity for modules are independent. In particular, we construct a commutative Noetherian local ring and a reflexive -module $…
Open loci of graded modules
Christel Rotthaus, Liana M. Sega
Let $A=\oplus_{i\in \nn}A_i$ be an excellent homogeneous Noetherian graded ring and let $M=\oplus_{n\in \zz}M_n$ be a finitely generated graded -module. We consider as a mod…
Nonvanishing cohomology and classes of Gorenstein rings
David A. Jorgensen, Liana M. Sega
We give counterexamples to the following conjecture of Auslander: given a finitely generated module over an Artin algebra , there exists a positive integer such that f…
Vanishing of cohomology over Gorenstein rings of small codimension
Liana M Sega
We prove that if M, N are finite modules over a Gorenstein local ring R of codimension at most 4, then the vanishing of Ext^n_R(M,N) for n\gg 0 is equivalent to the vanishing of Ex…