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Mappings Preserving Identities Given by Unitaries

  • Jiankui Li,
  • Kaijia Luo

摘要

Let A be a unital semisimple Banach \(*\) -algebra whose centre is denoted by Z(A), and let m be a fixed element in Z(A). Let fg be two continuous linear mappings on A satisfying the identity \(f(u)u^{*}+u^{*}f(u)+u{g(u)}^{*}+{g(u)}^{*}u=m\) f ( u ) u + u f ( u ) + u g ( u ) + g ( u ) u = m for each unitary element u in A. Then we prove that there exist two derivations \(d_{1},d_{2}\) d 1 , d 2 such that \(f(a)=d_{1}(a)+f(1)a, g(a)=d_{2}(a)+g(1)a\) f ( a ) = d 1 ( a ) + f ( 1 ) a , g ( a ) = d 2 ( a ) + g ( 1 ) a and \(d_{1}(a^{*})={d_{2}(a)}^{*}\) d 1 ( a ) = d 2 ( a ) for each \(a\in A\) a A . Let T be a conjugate linear mapping which is ternary derivable at the unit element from a unital \(C^*\) C -algebra into its dual space. We establish the automatic continuity of any such a mapping T.