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We investigate the shape of the numerical range for composition operators on the Hardy space H of the unit disc. As is usually the case when one studies composition operators, interesting questions arise from the interplay between the theories of analytic functions and linear operators.

Let Π = {z ∈ C : Imz > 0} be the upper half-plane in the complex plane. This paper characterizes the bounded products of differentiation operator and composition operator acting from the weighted Bergman space Aα(Π) to the weighted-type space A∞(Π) and the Bloch-type space B∞(Π). Mathematics Subject Classification: Primary 47B38; Secondary 47B33, 47B37

We show that the L(w) operator norm of the composition M◦TΩ, where M is the maximal operator and TΩ is a rough homogeneous singular integral with angular part Ω ∈ L∞(Sn−1), depends quadratically on [w]A2 , and this dependence is sharp.

After it has been successfully done in probability and possibility theories, the paper is the first attempt to introduce the operator of composition also for belief functions. We prove that the proposed definition preserves all the necessary properties of the operator enabling us to define compositional models as an efficient tool for multidimensional models representation.

Published results show that various models may be obtained by combining parallel composition with probability and with or without non-determinism. In this paper we treat this problem in the setting of process algebra in the form of ACP. First, probabilities are introduced by an operator for the internal probabilistic choice. In this way we obtain the Basic Process Algebra with probabilistic cho...

We show that the symbol of a bounded composition operator on Wiener algebra Dirichlet series does not need to belong this algebra. Our example even gives an absolutely summing (hence compact) operator.

We unify the parallel composition rule of assumption-commitment speciications for respectively state-based and message-based concurrent processes. Without providing language-dependent deenitions, we rst assume that the model of a process can be given as a set of`sequences' (e.g., traces, state sequences). Then we assume the existence of a merging operator that captures the compositionality of t...

Rn×Rn S( x+ y 2 , η) e2iπ〈x−y, η〉 u(y) dy dη : such a linear operator extends as a continuous operator from S ′(Rn) to S(R) while, in the case when S ∈ S ′(Rn ×R) , one can still define Op(S) as a linear operator from S(R) to S ′(Rn) ; also, Op sets up an isometry from L(R×R) onto the space of Hilbert-Schmidt operators on L(R) . The sharp composition S1#S2 of two symbols, say lying in S(R×R) , ...

In this paper we study a process algebra whose semantics is based on true concurrency. In our model, actions are defined in terms of the resources they need to execute, which allows a simple definition of a weak sequential composition operator. This operator allows actions which do not share any resources to execute concurrently, while dependent actions have to occur sequentially. This weak seq...