“…When B is a complex unital Banach *-algebra, Cuntz (6) has shown that B is a C*-algebra in an equivalent norm if and only if Q{1, b) is a C*algebra in an equivalent norm for each self-adjoint b in B. However, the methods he uses do not generalize to the case of Banach Jordan algebras.…”
1. Introduction. Recently Kaplansky suggested the definition of a suitable Jordan analogue of B*-algebras, which we call J B*-algebras (see (10) and (11)). In this article, we give a characterization of those complex unital Banach Jordan algebras which are J B*-algebras in an equivalent norm. This is done by generalizing results of Bonsall ((3) and (4)) to give necessary and sufficient conditions on a real unital Banach Jordan algebra under which it is the self-adjoint part of a J B*-algebra in an equivalent norm. As a corollary we also obtain a characterization of the cones in a Banach Jordan algebra which are the set of positive elements of a J B*-algebra.
“…When B is a complex unital Banach *-algebra, Cuntz (6) has shown that B is a C*-algebra in an equivalent norm if and only if Q{1, b) is a C*algebra in an equivalent norm for each self-adjoint b in B. However, the methods he uses do not generalize to the case of Banach Jordan algebras.…”
1. Introduction. Recently Kaplansky suggested the definition of a suitable Jordan analogue of B*-algebras, which we call J B*-algebras (see (10) and (11)). In this article, we give a characterization of those complex unital Banach Jordan algebras which are J B*-algebras in an equivalent norm. This is done by generalizing results of Bonsall ((3) and (4)) to give necessary and sufficient conditions on a real unital Banach Jordan algebra under which it is the self-adjoint part of a J B*-algebra in an equivalent norm. As a corollary we also obtain a characterization of the cones in a Banach Jordan algebra which are the set of positive elements of a J B*-algebra.
“…Furthermore A. I. Loginov and V. S. Shulman [10] (see [15] and [16] for a more transparent presentation) proved the corresponding result for norm-closed J-symmetric algebras in Π k -spaces was obtained: a J-symmetric algebra A ⊂ B(H) has no invariant subspaces if and only if its norm-closure contains the algebra K(H). The proof is quite complicated and uses the striking theorem of J. Cuntz [4] about C * -equivalent Banach *-algebras.…”
Section: J-symmetric Algebras and Burnside-type Theoremsmentioning
We discuss Lomonosov's proof of the Pontryagin-Krein Theorem on invariant maximal nonpositive subspaces, prove the refinement of one theorem from [22] on common fixed points for a group of fractional-linear maps of operator ball and deduce its consequences. Some Burnside-type counterparts of the Pontryagin-Krein Theorem are also considered.
“…(Almost Hermitian representations constitute probably the largest class of representations for which such similarity exists.) The most decisive step for proving Theorem 4 is the result obtained in Theorem 3: irreducible, uniformly closed J-symmetric operator algebras on Π fc -spaces contain the algebra of all compact operators.This last result was announced in [24] and its proof is based on Cuntz's theorem [6] and on some techniques developed in [41].…”
Section: The General Case When N(s)mentioning
confidence: 99%
“…By Theorem 2, all these subalgebras are C*-equivalent. Cuntz [6] proved that a Banach *-algebra is C*-equivalent if the closed commutative *-subalgebra generated by any selfadjoint element of the algebra is C*-equivalent. Applying this result to the algebra £?, we obtain that it is C*-equivalent.…”
Section: Theorem 3 An Irreducible Uniformly Closed J-symmetric Opementioning
This paper studies almost Hermitian, J-symmetric representations of *-algebras on Π^-spaces. It applies the results obtained to the theory of *-derivations δ of C*-algebras implemented by symmetric operators 5.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.