Abstract

Let A be a C * -algebra of real rank zero and B be a C * -algebra with unit I.I t is shown that if φ : A -→ B is an additive mapping which satisfies |φ(A)φ(B) |≤ φ(|AB| )f or every A, B ∈ A+ and φ(A )= I for some A ∈ As withA �≤ 1, then the restriction of mapping φ to As is a Jordan homomorphism, where As denotes the set of all self-adjoint elements. We will also show that if φ is surjective preserving the product and an absolute value, then φ is a C-linear or C-antilinear *-homomorphism on A. MSC: Primary 47B49; Secondary 46L05; 47L30

Highlights

  • Introduction and preliminariesIn recent years, the subject of linear preserver problems is the focus of attention of many mathematicians, and much research has been going on in this area

  • The subject of linear preserver problems is the focus of attention of many mathematicians, and much research has been going on in this area

  • We say that a mapping φ : A –→ B is preserving absolute values of a product if |φ(A)φ(B)| = φ(|AB|) (resp. |φ(A)φ(B)| ≤ φ(|AB|)) for every A, B ∈ A, where |A| = A*A

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Summary

Introduction and preliminaries

The subject of linear preserver problems is the focus of attention of many mathematicians, and much research has been going on in this area. Let A and B be two C*-algebras with unit I. We say that a mapping φ : A –→ B is preserving Sub-preserving) absolute values of a product if |φ(A)φ(B)| = φ(|AB|) By a *-homomorphism we just mean a map φ : A –→ B which preserves the ring structure and for which φ(A*) = φ(A)* for every A ∈ A. *-homomorphism if it is R-linear, φ(A*) = φ(A)* and φ(A) = φ(A ) for all A ∈ A. We say a map φ : A → B is unital if φ(I) = I.

We define
Note that r is positive and r

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