We consider the relationship between the Haagerup constants for a C-algebra and its crossed product by an amenable group. We prove equality when the group is discrete, and deduce equality when the group is compact and abelian.

A sufficient condition that the product of two compact spaces has the property of weak approximation by points (briefly WAP) is given. It follows that the product of the unit interval with a compact WAP space is also a WAP space.

The extended Cuntz–Pimsner algebra E(H), introduced by Pimsner, is constructed from a Hilbert B, B–bimodule H over a C∗–algebra B. In this paper we investigate the Haagerup invariant Λ(·) for these algebras, the main result being that Λ(E(H)) = Λ(B) when H is full over B. In particular, E(H) has the completely bounded approximation property if and only if the same is true for B.

It is shown that sets of sampling for the Bergman space A2 have the “homogeneous approximation property” (HAP) and that sets with this property are sampling for A 2+E. In addition, previous results concerning the boundary behaviour of sampling sets are improved. ForO<p<oo, the Bergman space AP is the set of functions f analytic in the unit disk D = (2 : 1.~1 < 1) with where dA denotes Lebesgue ...

The Moving Finite Element method for the solution of time-dependent partial dierential equations is a numerical solution scheme which allows the automatic adaption of the nite element approximation space with time. An analysis of how this method models the steady solutions of a general class of parabolic linear source equations is presented. It is shown that the steady solutions of the Moving F...

We investigate a variant of the compact metric approximation property which, for subspaces X of c0 , is known to be equivalent to K(X), the space of compact operators on X , being an A/-ideal in the space of bounded operators on X , L{X). Among other things, it is shown that an arbitrary Banach space X has this property iff K(Y, X) is an Af-ideal in L(Y, X) for all Banach spaces Y and, furtherm...

An information-theoretic foundation for compound Poisson approximation limit theorems is presented, in analogy to the corresponding developments for the central limit theorem and for simple Poisson approximation. It is shown that the compound Poisson distributions satisfy a natural maximum entropy property within a natural class of distributions. Simple compound Poisson approximation bounds are...

We consider a semantics for a class-based object-oriented calculus based upon approximation; since in the context of LC such a semantics enjoys a strong correspondence with intersection type assignment systems, we also define such a system for our calculus and show that it is sound and complete. We establish the link with between type (we use the terminology predicate here) assignment and the a...

This is the first lecture in an introductory course on property testing. In this lecture, we introduce and illustrate the basic notions of property testing, emphasizing the themes of approximate decision and sub-linear complexity. In particular, we discuss the key role of representation, point out the focus on properties that are not fully symmetric, present the definitions of (standard) tester...

Property testing is a kind of randomized approximation in which one takes a small, random sample of a structure and wishes to determine whether the structure satisfies some property or is far from satisfying the property. We focus on the testability of classes of first-order expressible properties, and in particular, on the classification of prefixvocabulary classes for testability. The main re...