文摘
Let A and B be unital primitive Banach algebras with minimal idempotents. We prove that every surjective spectral isometry from A onto B is of the form λ Ψ where λ∈C with |λ|=1 and Ψ is either an isomorphism or an anti-isomorphism from A onto B. As an application we show that, for all Banach spaces X and Y , the spectral nearisometries and the approximate spectrum-preserving maps from L(X) onto L(Y) are perturbations of actual spectral isometries and spectrum-preserving maps, respectively.