Abstract
The paper was motivated by Kovacs’ paper (1973), Isaacs’ paper (1980) and a recent paper, due to Bresar et al. (2018), concerning Skolem-Noether algebras. Let K be a unital commutative ring, not necessarily a field. Given a unital K-algebra S, where K is contained in the center of S, n ∈ ℕ, the goal of this paper is to study the question: when can a homomorphism ϕ: Mn(K) → Mn(S) be extended to an inner automorphism of Mn(S)? As an application of main results presented in the paper, it is proved that if S is a semilocal algebra with a central separable subalgebra R, then any homomorphism from R into S can be extended to an inner automorphism of S.
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The authors would like to express their thanks to the referee for valuable suggestions and careful reading.
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The work of T.-K. Lee was supported in part by the Ministry of Science and Technology of Taiwan (MOST 107-2115-M-002-018-MY2) and the NCTS (Taipei Office).
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Han, J., Lee, TK. & Park, S. A Note on Skolem-Noether Algebras. Czech Math J 71, 137–154 (2021). https://doi.org/10.21136/CMJ.2020.0215-19
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DOI: https://doi.org/10.21136/CMJ.2020.0215-19
Keywords
- Skolem-Noether algebra
- (inner) automorphism
- matrix algebra
- central simple algebra
- central separable algebra
- semilocal ring
- unique factorization domain (UFD)
- stably finite ring
- Dedekind-finite ring