Rings that are Morita equivalent to their opposites

JOURNAL OF ALGEBRA

卷:430

Article

First, Uriya A.

关键词: Morita equivalence;    Anti-automorphism;    Involution;    Bilinear form;    General bilinear form;    Brauer group;    Azumaya algebra;    Corestriction;    Semilocal ring;   

DOI  :  10.1016/j.jalgebra.2015.01.026

来源: Elsevier

【 摘 要 】

We consider the following problem: Under what assumptions are one or more of the following equivalent for a ring R: (A) R is Morita equivalent to a ring with involution, (B) R is Morita equivalent to a ring with an anti-automorphism, (C) R is Morita equivalent to its opposite ring. The problem is motivated by a theorem of Saltman which roughly states that all conditions are equivalent for Azurnaya algebras. Based on the recent general bilinear forms of [10], we present a general machinery to attack the problem, and use it to show that (C) double left right arrow (B) when R is semilocal or Q-finite. Further results of similar flavor are also obtained, for example: If R is a semilocal ring such that M-n(R) has an involution, then M-2(R) has an involution, and under further mild assumptions, R itself has an involution. In contrast to that, we demonstrate that (B) (sic) (A). Our methods also give a new perspective on the Knus-Parimala-Srinivas proof of Saltman's Theorem. Finally, we give a method to test Azumaya algebras of exponent 2 for the existence of involutions, and use it to construct explicit examples of such algebras. (C) 2015 Elsevier Inc. All rights reserved.

【 授权许可】

Free