Derivation-like mappings for normal elements in prime rings with involution.
Let be a prime ring, a nonzero ideal of , a derivation of and fixed positive integers. (i) If for all , then is commutative. (ii) If and for all , then is commutative. Moreover, we also examine the case when is a semiprime ring.
Let be a prime ring of char with a nonzero derivation and let be its noncentral Lie ideal. If for some fixed integers , for all , then satisfies , the standard identity in four variables.
We define polynomial -identities for comodule algebras over a Hopf algebra and establish general properties for the corresponding -ideals. In the case is a Taft algebra or the Hopf algebra , we exhibit a finite set of polynomial -identities which distinguish the Galois objects over up to isomorphism.
Partially supported by grant RFFI 98-01-01020.Let Uc be the variety of associative algebras generated by the algebra of all upper triangular matrices, the field being arbitrary. We prove that the upper exponent of any subvariety V ⊂ Uc coincides with the lower exponent and is an integer.