Abstract
We investigate functors between abelian categories having a left adjoint and a right adjoint that are similar (these functors are called quasi-Frobenius functors). We introduce the notion of a quasi-Frobenius bimodule and give a characterization of these bimodules in terms of quasi-Frobenius functors. Some applications to corings and graded rings are presented. In particular, the concept of quasi-Frobenius homomorphism of corings is introduced. Finally, a version of the endomorphism ring Theorem for quasi-Frobenius extensions in terms of corings is obtained.
ACKNOWLEDGMENTS
F. Castaño Iglesias' research was supported by projects MTM2008-03339 from MEC and DGI (Spain) and P07-FQM-03128 of Junta de Andalucia.
C. Nǎstǎsescu's research was supported by Grant ID-1904, contract 479/13.01.2009 of CNCSIS.
J. Vercruysse is Postdoctoral Fellow of the Fund for Scientific Research–Flanders (Belgium) (F.W.O.–Vlaanderen).
Notes
Communicated by C. Cibils.