Topological semigroups with one-sided units

One-Sided Interval Trees

We give an alternative treatment and extension of some results of Itoh and Mahmoud on one-sided interval trees. The proofs are based on renewal theory, including a case with mixed multiplicative and additive renewals.

On the topological boundary of the one-sided spectrum

It is well-known that the topological boundary of the spectrum of an operator is contained in the approximate point spectrum. We show that the one-sided version of this result is not true. This gives also a negative answer to a problem of Schmoeger. Denote by L(X) the algebra of all bounded linear operators acting in a Banach space X. For T ∈ L(X) denote by σ(T ), σl(T ) and σπ(T ) the spectrum...

On Computing the Topological Entropy of One-sided Cellular Automata

Morita Equivalence of Semigroups with Local Units

We prove that two semigroups with local units are Morita equivalent if and only if they have a joint enlargement. This approach to Morita theory provides a natural framework for understanding McAlister’s theory of the local structure of regular semigroups. In particular, we prove that a semigroup with local units is Morita equivalent to an inverse semigroup precisely when it is a regular locall...

The Structure of Topological Semigroups

The title of this address might incline one to the notion that here is to be found a small number of large theorems. To the contrary, I shall talk about a large number of small theorems. Actually, there does not exist a t this time any corpus of information to which the title "structure of topological semigroups" is in any fashion applicable. Whether such a body of theorems will ever exist is a...