English

Automorphisms and derivations of finite-dimensional algebras

Rings and Algebras 2021-12-01 v1

Abstract

Let AA be a finite-dimensional algebra over a field FF with char(F)2(F)\ne 2. We show that a linear map D:AAD:A\to A satisfying xD(x)x[A,A]xD(x)x\in [A,A] for every xAx\in A is the sum of an inner derivation and a linear map whose image lies in the radical of AA. Assuming additionally that AA is semisimple and char(F)3(F)\ne 3, we show that a linear map T:AAT:A\to A satisfies T(x)3x3[A,A]T(x)^3- x^3 \in [A,A] for every xAx\in A if and only if there exist a Jordan automorphism JJ of AA lying in the multiplication algebra of AA and a central element α\alpha satisfying α3=1\alpha^3=1 such that T(x)=αJ(x)T(x)=\alpha J(x) for all xAx\in A. These two results are applied to the study of local derivations and local (Jordan) automorphisms. In particular, the second result is used to prove that every local Jordan automorphism of a finite-dimensional simple algebra AA (over a field FF with char(F)2,3(F)\ne 2,3) is a Jordan automorphism.

Keywords

Cite

@article{arxiv.2111.15237,
  title  = {Automorphisms and derivations of finite-dimensional algebras},
  author = {Matej Brešar},
  journal= {arXiv preprint arXiv:2111.15237},
  year   = {2021}
}

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15 pages