New associative and nonassociative Gelfand-Naimark theorems.
Nonassociative algebras with submultiplicative bilinear form.
Nonassociative normed algebras: geometric aspects
Introduction. The aim of this paper is to review some relevant results concerning the geometry of nonassociative normed algebras, without assuming in the first instance that such algebras satisfy any familiar identity, like associativity, commutativity, or Jordan axiom. In the opinion of the author, the most impressive fact in this direction is that most of the celebrated natural geometric conditions that can be required for associative normed algebras, when imposed on a general nonassociative...
Nonassociative real H*-algebras.
We prove that, if A denotes a topologically simple real (non-associative) H*-algebra, then either A is a topologically simple complex H*-algebra regarded as real H*-algebra or there is a topologically simple complex H*-algebra B with *-involution τ such that A = {b ∈ B : τ(b) = b*}. Using this, we obtain our main result, namely: (algebraically) isomorphic topologically simple real H*-algebras are actually *-isometrically isomorphic.
Noncommutative function theory and unique extensions
We generalize, to the setting of Arveson’s maximal subdiagonal subalgebras of finite von Neumann algebras, the Szegő -distance estimate and classical theorems of F. and M. Riesz, Gleason and Whitney, and Kolmogorov. As a byproduct, this completes the noncommutative analog of the famous cycle of theorems characterizing the function algebraic generalizations of from the 1960’s. A sample of our other results: we prove a Kaplansky density result for a large class of these algebras, and give a necessary...
Non-commutative moment problems.
Nonlinear -Lie higher derivations of standard operator algebras
Let be an infinite-dimensional complex Hilbert space and be a standard operator algebra on which is closed under the adjoint operation. It is shown that every nonlinear -Lie higher derivation of is automatically an additive higher derivation on . Moreover, is an inner -higher derivation.
Non-normal elements in Banach *-algebras
Let A be a Banach *-algebra with an identity, continuous involution, center Z and set of self-adjoint elements Σ. Let h ∈ Σ. The set of v ∈ Σ such that (h + iv)ⁿ is normal for no positive integer n is dense in Σ if and only if h ∉ Z. The case where A has no identity is also treated.
Normal cones and --convex structure
The notion of normal cones is used to characterize --convex algebras among unital, symmetric and complete -convex algebras.
Normed algebras with involution.
Note on a general dilation theorem