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Given an irreducible non-spherical non-affine (possibly non-proper) building $X$, we give sufficient conditions for a group $G < \Aut(X)$ to admit an infinite-dimensional space of non-trivial quasi-morphisms. The result applies to all…

Group Theory · Mathematics 2009-04-28 Pierre-Emmanuel Caprace , Koji Fujiwara

We determine the decomposition numbers of the partition algebra when the characteristic of the ground field is zero or larger than the degree of the partition algebra. This will allow us to determine for which exact values of the parameter…

Representation Theory · Mathematics 2014-03-21 Armin Shalile

In this paper we analyze the structure of some sets of non-commutative moments of elements in a finite von Neumann algebra M. If the fundamental group of M is R_+\{0}, then the moment sets are convex, and if M is isomorphic to M tensor M,…

Operator Algebras · Mathematics 2007-05-23 Florin Radulescu

If H is a flat group of automorphisms of finite rank n of a totally disconnected, locally compact group G, then each orbit of H in the metric space B(G) of compact, open subgroups of G is quasi-isometric to n-dimensional euclidean space. In…

Group Theory · Mathematics 2008-08-01 Udo Baumgartner , Günter Schlichting , George A. Willis

Commutative Hilbertian Frobenius algebras are those commutative semi-group objects in the monoidal category of Hilbert spaces, for which the Hilbert adjoint of the multiplication satisfies the Frobenius compatibility relation, that is, this…

Functional Analysis · Mathematics 2020-03-10 Laurent Poinsot

A finite-dimensional algebra $A$ over an algebraically closed field $K$ is called periodic if it is periodic under the action of the syzygy operator in the category of $A-A-$ bimodules. The periodic algebras are self-injective and occur…

Representation Theory · Mathematics 2017-10-31 Karin Erdmann , Andrzej Skowroński

A subspace Y of a separable metrizable space X is separable, but without X metrizable this is not true even If Y is a closed linear subspace of a topological vector space X. K.H. Hofmann and S.A. Morris introduced the class of pro-Lie…

General Topology · Mathematics 2015-01-14 Arkady Leiderman , Sidney A. Morris , Mikhail G. Tkachenko

We generalize the notions of the Futaki invariant and extremal vector field of a compact K\"ahler manifold to the general almost-Kahler case and show the periodicity of the extremal vector field when the symplectic form represents an…

Differential Geometry · Mathematics 2010-04-22 Mehdi Lejmi

Let G be a second countable, locally compact group and let f be a continuous Herz-Schur multiplier on G. Our main result gives the existence of a (not necessarily uniformly bounded) strongly continuous representation on a Hilbert space,…

Representation Theory · Mathematics 2010-01-05 Troels Steenstrup

We study the algebra $\mathfrak{M}^{\infty,\mathrm{dec}}(G)$ of decomposable Fourier multipliers on the group von Neumann algebra $\mathrm{VN}(G)$ of a locally compact group $G$, and its relation to the Fourier-Stieltjes algebra…

Functional Analysis · Mathematics 2025-04-01 Cédric Arhancet , Christoph Kriegler

We use the theory of cubic structures to give a fixed point Riemann-Roch formula for the equivariant Euler characteristics of coherent sheaves on projective flat schemes over Z with a tame action of a finite abelian group. This formula…

Number Theory · Mathematics 2007-05-23 T. Chinburg , G. Pappas , M. Taylor

We study a particular class of representations from the fundamental groups of punctured spheres $\Sigma_{0,n}$ to the group $\text{PSL} (2,\mathbb R)$ (and their moduli spaces), that we call \emph{super-maximal}. Super-maximal…

Geometric Topology · Mathematics 2016-04-04 Bertrand Deroin , Nicolas Tholozan

We define a notion of modular forms of half-integral weight on the quaternionic exceptional groups. We prove that they have a well-behaved notion of Fourier coefficients, which are complex numbers defined up to multiplication by $\pm 1$. We…

Number Theory · Mathematics 2022-09-20 Spencer Leslie , Aaron Pollack

We give a partial solution to a long-standing open problem in the theory of quantum groups, namely we prove that all finite-dimensional representations of a wide class of locally compact quantum groups factor through matrix quantum groups…

Operator Algebras · Mathematics 2019-01-28 Biswarup Das , Matthew Daws , Pekka Salmi

In this article we introduce and study uniform and non-uniform approximate lattices in locally compact second countable (lcsc) groups. These are approximate subgroups (in the sense of Tao) which simultaneously generalize lattices in lcsc…

Group Theory · Mathematics 2018-11-14 Michael Björklund , Tobias Hartnick

We continue in this paper the study of locally minimal groups started in \cite{LocMin}. The minimality criterion for dense subgroups of compact groups is extended to local minimality. Using this criterion we characterize the compact abelian…

General Topology · Mathematics 2010-06-29 Lydia Aussenhofer , María Jesús Chasco , Dikran Dikranjan , Xabier Domínguez

We study the unilateral shift (of arbitrary countable multiplicity) as a Hilbert module over the disc algebra and the associated extension groups. In relation with the problem of determining whether this module is projective, we consider a…

Operator Algebras · Mathematics 2014-05-23 Raphaël Clouâtre

Given a variety of universal algebras. A method is suggested for describing automorphisms of a category of free algebras of this variety. Applying this general method all automorphisms of such categories are found in two cases: 1) for the…

Rings and Algebras · Mathematics 2007-05-23 Boris Plotkin , Grigori Zhitomirski

We provide a geometric characterization of manifolds of dimension 3 with fundamental groups of which all conjugacy classes except 1 are infinite, namely of which the von Neumann algebras are factors of type $II_1$: they are essentially the…

Group Theory · Mathematics 2012-02-21 Pierre de la Harpe , Jean-Philippe Preaux

We study the Fourier--Stieltjes algebra of Roelcke precompact, non-archimedean, Polish groups and give a model-theoretic description of the Hilbert compactification of these groups. We characterize the family of such groups whose…

Logic · Mathematics 2017-10-23 Itaï Ben Yaacov , Tomás Ibarlucía , Todor Tsankov