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    Maps preserving peripheral spectrum of generalized products of operators

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    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 kβ‰₯2k\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 T1βˆ—T2βˆ—β‹―βˆ—Tk=Ti1Ti2β‹―TimT_1* T_2*\cdots* T_k=T_{i_1}T_{i_2}\cdots T_{i_m} on elements in Ai\mathcal{A}_i. Let Ξ¦:A1β†’A2\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 Ξ¦\Phi satisfies that σπ(Ξ¦(A1)βˆ—β‹―βˆ—Ξ¦(Ak))=σπ(A1βˆ—β‹―βˆ—Ak)\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 Ξ¦\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 A↦cUAUβˆ—A\mapsto cUAU^* or A↦cUAtUβˆ—A\mapsto cUA^tU^*, where U∈B(H,K)U\in\mathcal{B}(H,K) is a unitary operator, c∈{1,βˆ’1}c\in\{1,-1\}.Comment: 17 page
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