Deformation of involution and multiplication in a $C^*$-algebra
Studia Mathematica, Tome 215 (2013) no. 1, pp. 31-37

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We investigate the deformations of involution and multiplication in a unital $C^*$-algebra when its norm is fixed. Our main result is to present all multiplications and involutions on a given $C^*$-algebra $\mathcal {A}$ under which $\mathcal {A}$ is still a $C^*$-algebra when we keep the norm unchanged. For each invertible element $a\in \mathcal {A}$ we also introduce an involution and a multiplication making $\mathcal {A}$ into a $C^*$-algebra in which $a$ becomes a positive element. Further, we give a necessary and sufficient condition for the center of a unital $C^*$-algebra $\mathcal {A}$ to be trivial.
DOI : 10.4064/sm215-1-3
Keywords: investigate deformations involution multiplication unital * algebra its norm fixed main result present multiplications involutions given * algebra mathcal under which mathcal still * algebra keep norm unchanged each invertible element mathcal introduce involution multiplication making mathcal * algebra which becomes positive element further necessary sufficient condition center unital * algebra mathcal trivial

H. Najafi 1 ; M. S. Moslehian 1

1 Department of Pure Mathematics Center of Excellence in Analysis on Algebraic Structures (CEAAS) Ferdowsi University of Mashhad P.O. Box 1159 Mashhad 91775, Iran
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H. Najafi; M. S. Moslehian. Deformation of involution and multiplication in a $C^*$-algebra. Studia Mathematica, Tome 215 (2013) no. 1, pp. 31-37. doi: 10.4064/sm215-1-3

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