 
Summary: Journal of Algebra 256 (2002) 111125
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Semisimple strongly graded rings
E. Aljadeff,a,,1
Y. Ginosar,b,2
and Á. del Río c,3
a Department of Mathematics, TechnionIsrael Institute of Technology, 32000 Haifa, Israel
b Department of Mathematics, Ben Gurion University, 84105 Beer Sheva, Israel
c Departamento de Matemáticas, Universidad de Murcia, 30100 Murcia, Spain
Received 7 May 2001
Communicated by Kent R. Fuller
1. Introduction
Let G be a finite group and R a strongly Ggraded ring. The question of when
R is semisimple (meaning in this paper semisimple artinian) has been studied by
several authors. The most classical result is Maschke's Theorem for group rings.
For crossed products over fields there is a satisfactory answer given by Aljadeff
and Robinson [3]. Another partial answer for skew group rings was given by
Alfaro et al. [1]. A reduction of the problem to crossed products over division
rings was first given by Jespers and Okni´nski [10] and a more constructive version
was given by Haefner and del Río [8]. So, in order to give a complete answer to
