English

Linear isometries between real JB*-triples and C*-algebras

Operator Algebras 2013-09-17 v1

Abstract

Let T:ABT: A\to B be a (not necessarily surjective) linear isometry between two real JB^*-triples. Then for each aAa\in A there exists a tripotent uau_a in the bidual, B,B'', of BB such that \begin{enumerate}[(a)(a)] \item {ua,T({f,g,h}),ua}={ua,{T(f),T(g),T(h)},ua}\{u_a,T(\{f,g,h\}),u_a\}=\{u_a,\{T(f),T(g),T(h)\},u_a\}, for all f,g,hf,g,h in the real JB^*-subtriple, Aa,A_a, generated by aa; \item The mapping {ua,T(),ua}:AaB\{u_a,T(\cdot),u_a\} :A_a\rightarrow B'' is a linear isometry. \end{enumerate} Furthermore, when BB is a real C^*-algebra, the projection p=pa=uauap=p_a= u_a^* u_a satisfies that T()p:AaBT(\cdot)p :A_a\rightarrow B'' is an isometric triple homomorphism. When AA and BB are real C^*-algebras and AA is abelian of real type, then there exists a partial isometry uBu\in B'' such that the mapping T()uu:ABT(\cdot)u^*u :A\rightarrow B'' is an isometric triple homomorphism. These results generalise, to the real setting, some previous contributions due to C.-H. Chu and N.-C. Wong, and C.-H. Chu and M. Mackey in 2004 and 2005. We give an example of a non-surjective real linear isometry which cannot be complexified to a complex isometry, showing that the results in the real setting can not be derived by a mere complexification argument.

Keywords

Cite

@article{arxiv.1309.3838,
  title  = {Linear isometries between real JB*-triples and C*-algebras},
  author = {Maria Apazoglou and Antonio M. Peralta},
  journal= {arXiv preprint arXiv:1309.3838},
  year   = {2013}
}

Comments

to appear in Quart. J. Math

R2 v1 2026-06-22T01:27:32.864Z