Let X be a complex Banach space. If 8: B(X) Γ B(X) is a surjective linear map such that A and 8(A) have the same spectral radius for every A # B(X), then 8=c3 where 3 is either an algebra-automorphism or an antiautomorphism of B(X) and c is a complex constant such that |c|=1.
Linear operators preserving the sign-real spectral radius
β Scribed by Bojana Zalar
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 105 KB
- Volume
- 301
- Category
- Article
- ISSN
- 0024-3795
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β¦ Synopsis
Define the sign-real spectral radius of a real n Γ n matrix A as Ο s 0 (A) = max SβS Ο 0 (SA), where Ο 0 (A) = max{|Ξ»|; Ξ» a real eigenvalue of A} is the real spectral radius of A and S denotes the set of signature matrices, i.e. S = {S; |S| = I}, the absolute value of matrices being meant entrywise. In this paper we show that linear invertible operators F on the space of n Γ n real matrices M n (R) preserving the sign-real spectral radius are exactly the operators of the form F (A) = P T D -1 SA (T) DP with P a permutation matrix, D a diagonal matrix and S a signature matrix.
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