1,464,220 research outputs found
Twisted actions and regular Fell bundles over inverse semigroups
We introduce a new notion of twisted actions of inverse semigroups and show
that they correspond bijectively to certain regular Fell bundles over inverse
semigroups, yielding in this way a structure classification of such bundles.
These include as special cases all the stable Fell bundles.
Our definition of twisted actions properly generalizes a previous one
introduced by Sieben and corresponds to Busby-Smith twisted actions in the
group case. As an application we describe twisted etale groupoid C*-algebras in
terms of crossed products by twisted actions of inverse semigroups and show
that Sieben's twisted actions essentially correspond to twisted etale groupoids
with topologically trivial twists.Comment: 35 page
Deformations of Lie brackets: cohomological aspects
We introduce a new cohomology for Lie algebroids, and prove that it provides
a differential graded Lie algebra which ``controls'' deformations of the
structure bracket of the algebroid. We also have a closer look at various
special cases such as Lie algebras, Poisson manifolds, foliations, Lie algebra
actions on manifolds.Comment: 17 pages, Revised version: small corrections, more references adde
Circle actions on a quantum Seifert manifold
The quotients of a (non-orientable) quantum Seifert manifold by circle
actions are described. In this way quantum weighted real projective spaces that
include the quantum disc and the quantum real projective space as special cases
are obtained. Bounded irreducible representations of the coordinate algebras
and the K-groups of the algebras of continuous functions on quantum weighted
real projective spaces are presented.Comment: 9 page
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