Abstract
LetA andB be unital Banach algebras withA a subalgebra ofB. Denote the algebra of alln xn matrices with entries fromA byM n (A). In this paper we prove some results concerning the open question: IfA is inverse closed inB, then isM n (A) inverse closed inM n (B)? We also study related questions in the setting where A is a symmetric Banach *-algebra.
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Dedicated to Professor Ashoke K. Roy on his retirement.
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Barnes, B.A. Questions concerning matrix algebras and invariance of spectrum. Proc. Indian Acad. Sci. (Math. Sci.) 113, 71–76 (2003). https://doi.org/10.1007/BF02829680
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DOI: https://doi.org/10.1007/BF02829680