Monoid Extensions, Relaxed Actions and Cohomology
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Authors
Faul, Peter
Abstract
In this thesis a particular class of monoid extensions are studied and characterized, the weakly Schreier split extensions. It is demonstrated that both Artin glueings of frames and λ-semidirect products of inverse semigroups are examples of these extensions. The characterization is given in terms of a generalization of an action. This makes the theory amenable to cohomological ideas. Specifically, a new class of extensions called cosetal extensions are introduced and characterized. When parameterized by this new notion of action, a Baer sim may be defined in these extensions giving rise to an analogue of the second cohomology group. Finally, a connection is made to the setting of toposes, exploiting the link between toposes and frames.
Description
Date
2020-12-01
Advisors
Johnstone, Peter
Keywords
Monoid, Extension, Schreier, Topos, Frame, Artin glueing
Qualification
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge