Baer semigroups and lattices

Daggers, Kernels, Baer *-semigroups, and Orthomodularity

We discuss issues related to constructing an orthomodular structure from an object in a category. In particular, we consider axiomatics related to Baer *-semigroups, partial semigroups, and various constructions involving dagger categories, kernels, and biproducts.

On Maximal Subsemigroups of Partial Baer-Levi Semigroups

Suppose that X is an infinite set with |X| ≥ q ≥ א0 and I X is the symmetric inverse semigroup defined on X. In 1984, Levi and Wood determined a class of maximal subsemigroups MA using certain subsets A of X of the Baer-Levi semigroup BL q {α ∈ I X : dom α X and |X \ Xα| q}. Later, in 1995, Hotzel showed that there are many other classes of maximal subsemigroups of BL q , but these are far more...

On Lattices of Varieties of Restriction Semigroups

The left restriction semigroups have arisen in a number of contexts, one being as the abstract characterization of semigroups of partial maps, another as the ‘weakly left E-ample’ semigroups of the ‘York school’, and, more recently as a variety of unary semigroups defined by a set of simple identities. We initiate a study of the lattice of varieties of such semigroups and, in parallel, of their...

Extensions of Baer and quasi-Baer modules

Orthomodular lattices, Foulis Semigroups and Dagger Kernel Categories

This paper is a sequel to [19] and continues the study of quantum logic via dagger kernel categories. It develops the relation between these categories and both orthomodular lattices and Foulis semigroups. The relation between the latter two notions has been uncovered in the 1960s. The current categorical perspective gives a broader context and reconstructs this relationship between orthomodula...