On Markushevich bases in preduals of von Neumann algebras

We prove that the predual of any von Neumann algebra is 1-Plichko, i.e., it has a countably 1-norming Markushevich basis. This answers a question of the third author who proved the same for preduals of semifinite von Neumann algebras. As a corollary we obtain an easier proof of a result of U. Haagerup that the predual of any von Neumann algebra enjoys the separable complementation property. We further prove that the selfadjoint part of the predual is 1-Plichko as well.     

Compact range property and operators on -algebras

We prove that a Banach space has the compact range property (CRP) if and only if, for any given -algebra , every absolutely summing operator from into is compact. Related results for -summing operators () are also discussed as well as operators on non-commutative -spaces and -summing operators.

     

On the geometry of von Neumann algebra preduals

Let \(M\) be a von Neumann algebra and let \(M_\star \) be its (unique) predual. We study when for every \(\varphi \in M_\star \) there exists \(\psi \in M_\star \) solving the equation \(\Vert \varphi \pm \psi \Vert =\Vert \varphi \Vert =\Vert \psi \Vert \) . This is the case when \(M\) does not contain type I nor type III \(_1\) factors as direct summands and it is false at least for the unique hyperfinite type III \(_1\) factor. We also characterize this property in terms of the existence of centrally symmetric curves in the unit sphere of \(M_\star \) of length \(4\) . An approximate result valid for all diffuse von Neumann algebras allows to show that the equation has solution for every element in the ultraproduct of preduals of diffuse von Neumann algebras and, in particular, the dual von Neumann algebra of such ultraproduct is diffuse. This shows that the Daugavet property and the uniform Daugavet property are equivalent for preduals of von Neumann algebras.     

have the Dunford-Pettis property

Denote by either the disc algebra , or the space of bounded analytic functions on the disc, or any of their even duals. Then has the Dunford-Pettis property.

     

On the split property for inclusions of -algebras

A characterization of the quasi-split property for an inclusion of -algebras in terms of the metrically nuclear maps is established. This result extends the known characterization relative to inclusions of -factors. An application to type von Neumann algebras is also presented.

     

Asymptotic behavior of Markov semigroups on preduals of von Neumann algebras

We develop a new approach for investigation of asymptotic behavior of Markov semigroup on preduals of von Neumann algebras. With using of our technique we establish several results about mean ergodicity, statistical stability, and constrictiviness of Markov semigroups.     

On the Dunford-Pettis property of the tensor product of spaces

In this paper we characterize those compact Hausdorff spaces such that (and ) have the Dunford-Pettis Property, answering thus in the negative a question posed by Castillo and González who asked if and have this property.

     

The Dunford-Pettis property in Jb*-Triples

JB*-triples occur in the study of bounded symmetric domainsin several complex variables and in the study of contractiveprojections on C*-algebras. These spaces are equipped with aternary product {·,·,·}, the Jordan tripleproduct, and are essentially geometric objects in that the linearisometries between them are exactly the linear bijections preservingthe Jordan triple product (cf. [23]).     

The Dunford-Pettis property is not a three-space property

An example of a Banach spaceX is shown which does not have the Dunford-Pettis property, while some subspaceY and the corresponding quotientX/Y have the hereditary Dunford-Pettis property.     

Residually finite dimensional and AF-embeddable -algebras

We show that every separable nuclear residually finite dimensional -algebras satisfying the Universal Coefficient Theorem can be embedded into a unital separable simple AF-algebra.

     

The fixed point property in -triples and preduals of -triples

We prove that for every member X in the class of real or complex JB^*-triples or preduals of JBW^*-triples, the following assertions are equivalent:

(1) X has the fixed point property.

(2) X has the super fixed point property.

(3) X has normal structure.

(4) X has uniform normal structure.

(5) The Banach space of X is reflexive.

As a consequence, a real or complex C^*-algebra or the predual of a real or complex W^*-algebra having the fixed point property must be finite-dimensional.

A von Neumann type inequality for certain domains in

Strict contractions on a Hilbert space have a functional calculus with functions that are analytic in the unit disc of the complex plane; an estimate of the norm is then provided by von Neumann's inequality. We consider functions that satisfy related inequalities with respect to multioperators connected to certain domains in ; a representation formula and a Nevanlinna-Pick type theorem are obtained.

     

Wigner's theorem in Hilbert -algebras of compact operators

Let be a Hilbert -module over the -algebra of all compact operators on a Hilbert space. It is proved that any function which preserves the absolute value of the -valued inner product is of the form , where is a phase function and is an -linear isometry. The result generalizes Molnár's extension of Wigner's classical unitary-antiunitary theorem.

     

Amenability and exactness for dynamical systems and their -algebras

We study the relations between amenability (resp. amenability at infinity) of -dynamical systems and equality or nuclearity (resp. exactness) of the corresponding crossed products.

     

Topological entropy, embeddings and unitaries in nuclear quasidiagonal -algebras

Using topological entropy of automorphisms of -algebras, it is shown that some important facts from the theory of AF algebras do not carry over to the class of algebras.

It is shown that in general one cannot perturb a basic building block into a larger one which almost contains it. The same entropy obstruction used to prove this fact also provides a new obstruction to the known fact that two injective homomorphisms from a building block into an algebra need not differ by an (inner) automorphism when they agree on K-theory.