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Maps preserving peripheral spectrum of generalized products of operators

Functional Analysis 2013-05-31 v1 Operator Algebras

Abstract

Let A1\mathcal{A}_1 and A2\mathcal{A}_2 be standard operator algebras on complex Banach spaces X1X_1 and X2X_2, respectively. For k2k\geq2, let (i1,...,im)(i_1,...,i_m) be a sequence with terms chosen from {1,,k}\{1,\ldots,k\}, and assume that at least one of the terms in (i1,,im)(i_1,\ldots,i_m) appears exactly once. Define the generalized product T1T2Tk=Ti1Ti2TimT_1* T_2*\cdots* T_k=T_{i_1}T_{i_2}\cdots T_{i_m} on elements in Ai\mathcal{A}_i. Let Φ:A1A2\Phi:\mathcal{A}_1\rightarrow\mathcal{A}_2 be a map with the range containing all operators of rank at most two. We show that Φ\Phi satisfies that σπ(Φ(A1)Φ(Ak))=σπ(A1Ak)\sigma_\pi(\Phi(A_1)*\cdots*\Phi(A_k))=\sigma_\pi(A_1*\cdots* A_k) for all A1,,AkA_1,\ldots, A_k, where σπ(A)\sigma_\pi(A) stands for the peripheral spectrum of AA, if and only if Φ\Phi is an isomorphism or an anti-isomorphism multiplied by an mmth root of unity, and the latter case occurs only if the generalized product is quasi-semi Jordan. If X1=HX_1=H and X2=KX_2=K are complex Hilbert spaces, we characterize also maps preserving the peripheral spectrum of the skew generalized products, and prove that such maps are of the form AcUAUA\mapsto cUAU^* or AcUAtUA\mapsto cUA^tU^*, where UB(H,K)U\in\mathcal{B}(H,K) is a unitary operator, c{1,1}c\in\{1,-1\}.

Keywords

Cite

@article{arxiv.1305.7100,
  title  = {Maps preserving peripheral spectrum of generalized products of operators},
  author = {Wen Zhang and Jinchuan Hou},
  journal= {arXiv preprint arXiv:1305.7100},
  year   = {2013}
}

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17 pages