On $H$-simple not necessarily associative algebras

An algebra A with a generalized H-action is a generalization of an H-module algebra where H is just an associative algebra with 1 and a relaxed compatibility condition between the multiplication in A and the H-action on A holds. At first glance this notion may appear too general, however it enables to work with algebras endowed with various kinds of additional structures (e.g. (co)module algebras over Hopf algebras, graded algebras, algebras with an action of a (semi)group by (anti)endomorphisms). This approach proves to be especially fruitful in the theory of polynomial identities. We show that if A is a finite dimensional (not necessarily associative) algebra over a field of characteristic 0 and A is simple with respect to a generalized H-action, then there exists an exponent of the codimension growth of polynomial H-identities of A. In particular, if A is a finite dimensional (not necessarily group graded) graded-simple algebra, then there exists an exponent of the codimension growth of graded polynomial identities of A. In addition, we study the free-forgetful adjunctions corresponding to (not necessarily group) gradings and generalized H-actions.Comment: 16 pages. The classification of Lie algebras simple with respect to a Taft algebra action has been moved to arXiv:1705.05809. The sections related to gradings by sets and free-forgetful adjunctions have been added. The misprints found by the referee have been corrected and several clarifications have been made. (To appear in Journal of Algebra and Its Applications.