Let H be a Hopf algebra and A an H-simple right H-comodule algebra. It is shown that under certain hypotheses every (H,A)-Hopf module is either projective or free as an A-module and A is either a quasi-Frobenius or a semisimple ring. As an application it is proved that every weakly finite (in particular, every finite dimensional) Hopf algebra is free both as a left and a right module over its f...

A Lie superalgebra is called quasi-Frobenius if it admits a closed anti-symmetric non-degenerate bilinear form. We study the notion of double extensions when form either orthosymplectic or periplectic. show that every satisfies certain conditions can be obtained as extension smaller superalgebra. classify all 4-dimensional superalgebras, and such superalgebras must solvable. [Formula: see text]...

The Bernstein-Sato polynomial is an important invariant of element or ideal in a ring power series characteristic zero, with interesting connections to various algebraic and topological aspects the singularities vanishing locus. Work Mustaţă, later extended by Bitoun third author, provides analogous theory for regular rings positive characteristic. In this paper, we extend singular ambient We e...