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In this talk, I will survey recent progress made on the classification of von Neumann algebras arising from countable groups and their actions on probability spaces. In particular, I will present the first results which provide classes of…

Operator Algebras · Mathematics 2012-12-04 Adrian Ioana

For every variety of algebras and every algebras in these variety we can consider an algebraic geometry. Algebras may be many sorted (not necessarily one sorted) algebras. A set of sorts is fixed for each variety. This theory can be applied…

Representation Theory · Mathematics 2007-05-23 B. Plotkin , A. Tsurkov

We utilize the structure of quasiautomorphic forms over an arbitrary Hecke triangle group to define a new vector analogue of an automorphic form. We supply a proof of the functional equations that hold for these functions modulo the group…

Number Theory · Mathematics 2026-01-01 Michael Andrew Henry

We study the scale function, space of directions and scale-multiplicative semigroups for restricted Burger-Mozes groups. We relate these general notions to intrinsic properties of the group. Among other things, we give a formula for the…

Group Theory · Mathematics 2019-12-06 Timothy P. Bywaters

We consider two operations on an edge of an embedded graph (or equivalently a ribbon graph): giving a half-twist to the edge and taking the partial dual with respect to the edge. These two operations give rise to an action of S_3^{|E(G)|},…

Combinatorics · Mathematics 2012-02-28 Joanna A. Ellis-Monaghan , Iain Moffatt

Motivated by logarithmic conformal field theory and Gromov-Witten theory, we introduce a notion of a twisted module of a vertex algebra under an arbitrary (not necessarily semisimple) automorphism. Its main feature is that the twisted…

Quantum Algebra · Mathematics 2016-06-17 Bojko Bakalov

In this article we will study semigroupoids, and more specifically inverse semigroupoids. These are a common generalization to both inverse semigroups and groupoids, and provide a natural language on which several types of dynamical…

Dynamical Systems · Mathematics 2019-02-26 Luiz Gustavo Cordeiro

For every smooth projective variety, we construct an action of the Heisenberg algebra on the direct sum of the Grothendieck groups of all the symmetric quotient stacks which contains the Fock space as a subrepresentation. The action is…

Algebraic Geometry · Mathematics 2015-01-29 Andreas Krug

The aim of this paper is to give a characterization in Hilbert spaces of the generators of $C_0$-semigroups associated with closed, sectorial forms in terms of the convergence of a generalized Trotter's product formula. In the course of the…

Functional Analysis · Mathematics 2007-05-23 Mate Matolcsi

The notion of a semitransitive binary action of a group $G$ on a topological space is introduced. A duality theorem is proved, establishing a bijective correspondence between semitransitive distributive binary $G$-spaces and topological…

General Topology · Mathematics 2026-05-05 Pavel S. Gevorgyan

We construct loops which are semidirect products of groups of affinities. As their elements in many cases one may take transversal subspaces of an affine space. In particular we obtain in this manner smooth loops having Lie groups of affine…

Group Theory · Mathematics 2015-07-01 Ágota Figula , Karl Strambach

We study the action of the mapping class group of an oriented genus g surface with n punctures and a disc removed on a Poisson algebra which arises in the combinatorial description of Chern-Simons gauge theory when the gauge group is a…

High Energy Physics - Theory · Physics 2009-11-10 C. Meusburger , B. J. Schroers

We use partial actions, as formalized by Exel, to construct various commensurating actions. We use this in the context of groups piecewise preserving a geometric structure, and we interpret the transfixing property of these commensurating…

Dynamical Systems · Mathematics 2025-02-18 Yves Cornulier

We study topological properties of semi-group actions on the circle by orientation-preserving homeomorhisms. We prove that a generic action either possesses a forward-invariant interval-domain (i.e. a finite union of disjoint circle arcs),…

Dynamical Systems · Mathematics 2018-04-04 Victor Kleptsyn , Yury Kudryashov , Alexey Okunev

We unify and generalize several approaches to constructing braid group representations from finite groups, using iterated twisted tensor products. Our results hint at a relationship between the braidings on the $G$-gaugings of a pointed…

Quantum Algebra · Mathematics 2019-06-20 Paul Gustafson , Andrew Kimball , Eric C. Rowell , Qing Zhang

This is the third paper of a series relating the equivariant twisted $K$-theory of a compact Lie group $G$ to the ``Verlinde space'' of isomorphism classes of projective lowest-weight representations of the loop groups. Here, we treat…

Algebraic Topology · Mathematics 2007-05-23 Daniel S. Freed , Michael J. Hopkins , Constantin Teleman

We prove that every partial action of an inverse semigroupoid on a set admits a universal globalization. Moreover, we show that our construction gives a reflector from the category of partial actions on the full subcategory of global…

Operator Algebras · Mathematics 2024-05-01 Paulinho Demeneghi , Felipe Augusto Tasca

In this paper, we construct a semigroup associated to an action of countable discrete group on a compact Hausdorff space, that can be regarded as a higher dimensional generalization of the type semigroup. Using this generalized type…

Dynamical Systems · Mathematics 2021-07-01 Xin Ma

In the context of ideally exact categories, we introduce the notions of internal coherent action and internal ideal action that generalise different aspects of unital actions of rings and algebras. We prove that every ideal action is…

Category Theory · Mathematics 2026-05-25 Manuel Mancini , Giuseppe Metere , Federica Piazza

Taking symmetric powers of varieties can be seen as a functor from the category of varieties to the category of varieties with an action by the symmetric group. We study a corresponding map between the Grothendieck groups of these…

Algebraic Geometry · Mathematics 2019-04-16 Daniel Bergh