engleski

Generalized bicircular projections on JB*-triples

Let $A$ be a JB*-triple and let $P : A \to A$ be a linear projection. It is proved that $P + \lambda (Id-P)$ is an isometry for some modulus one complex number $\lambda \neq 1$ if and only if either $\lambda = -1, $ or $P$ is hermitian. It is also proved that every rank one bicontractive projection on $A$ is hermitian. The particular case when $A$ is a C*-algebra is discussed through several examples.

JB*-triple ; C*-algebra ; generalized bicircular projection ; isometry ; bicontractive projection ; hermitian projection

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