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A topological group $G$ is extremely amenable if every continuous action of $G$ on a compact space has a fixed point. Using the concentration of measure techniques developed by Gromov and Milman, we prove that the group of automorphisms of…

Group Theory · Mathematics 2007-09-03 Thierry Giordano , Vladimir Pestov

Generalizing the notion of matched pair of groups, we define and study matched pairs of locally compact groupoids endowed with Haar systems, in order to give new examples of measured quantum groupoids.

Operator Algebras · Mathematics 2011-05-27 Jean-Michel Vallin

We analyze in this paper a random feature map based on a theory of invariance I-theory introduced recently. More specifically, a group invariant signal signature is obtained through cumulative distributions of group transformed random…

Machine Learning · Computer Science 2015-12-07 Youssef Mroueh , Stephen Voinea , Tomaso Poggio

We will show that group exactness is a von Neumann equivalence invariant. This result generalizes the previously known fact stating that group exactness is invariant under measure equivalence and W*-equivalence.

Operator Algebras · Mathematics 2023-09-06 Bat-Od Battseren

Coherence, the superposition of orthogonal quantum states, is indispensable in various quantum processes. Inspired by the polynomial invariant for classifying and quantifying entanglement, we first define polynomial coherence measure and…

Quantum Physics · Physics 2018-09-07 You Zhou , Qi Zhao , Xiao Yuan , Xiongfeng Ma

We show that topological amenability of an action of a countable discrete group on a compact space is equivalent to the existence of an invariant mean for the action. We prove also that this is equivalent to vanishing of bounded cohomology…

Group Theory · Mathematics 2010-04-05 Jacek Brodzki , Graham A. Niblo , Piotr Nowak , Nick Wright

The paper describes two possible ways of extending the definition of Haar measure to non-Hausdorff locally compact groups. The first one forces compact sets to be measurable: with this construction, a counterexample to the existence of the…

Group Theory · Mathematics 2023-09-15 Lisa Valentini

For a locally compact group, property RD gives a control on the convolution norm of any compactly supported measure in terms of the $L^2$-norm of its density and the diameter of its support. We give a complete classification of those Lie…

Group Theory · Mathematics 2007-05-23 I. Chatterji , Ch. Pittet , L. Saloff-Coste

We initiate a systematic investigation of group actions on compact medain algebras via the corresponding dynamics on their spaces of measures. We show that a probability measure which is invariant under a natural push forward operation must…

General Topology · Mathematics 2025-03-11 Uri Bader , Aviv Taller

Building on recent results regarding symmetric probabilistic constructions of countable structures, we provide a method for constructing probability measures, concentrated on certain classes of countably infinite structures, that are…

Logic · Mathematics 2015-11-24 Nathanael Ackerman , Cameron Freer , Jaroslav Nesetril , Rehana Patel

In [6], given a metrizable profinite group $G$, a cardinal invariant of the continuum $\mathfrak{fm}(G)$ was introduced, and a positive solution to the Haar Measure Problem for $G$ was given under the assumption that…

Logic · Mathematics 2019-06-21 Gianluca Paolini , Saharon Shelah

We prove that the measure algebra $M(G)$ of a locally compact group $G$ is Connes-amenable if and only if $G$ is amenable.

Functional Analysis · Mathematics 2007-05-23 Volker Runde

Given any amenable group $G$ (with a left Haar measure $|\cdot|$ or $dg$), we can select out a \textit{F{\o}lner subnet} $\{F_\theta,\theta\in\Theta\}$ from any left F{\o}lner net in $G$, which is \textit{$L^\infty$-admissible}, namely, for…

Dynamical Systems · Mathematics 2016-06-17 Xiongping Dai

We introduce the notion of Bartlett spectral measure for isometrically invariant random measures on proper metric commutative spaces. When the underlying Gelfand pair corresponds to a higher-rank, connected, simple matrix Lie group with…

Probability · Mathematics 2025-03-04 Michael Björklund , Mattias Byléhn

We characterize cohomogeneity one manifolds and homogeneous spaces with a compact Lie group action admitting an invariant metric with positive scalar curvature.

Differential Geometry · Mathematics 2022-03-14 Georg Frenck , Fernando Galaz-Garcia , Philipp Reiser

Let $K$ denote a simply connected compact Lie group and let $G=K^{\mathbb C}$, the complexification. It is known that there exists an $LK$ bi-invariant probability measure on a natural hyperfunction completion of the complex loop group…

Mathematical Physics · Physics 2025-12-23 Doug Pickrell

Relying on the notions of submodular function and partial metric, we introduce normed inverse semigroups as a generalization of normed groups and sup-semilattices equipped with an upper valuation. We define the property of skew-convexity…

Group Theory · Mathematics 2024-06-25 Paul Poncet

It is shown that a locally compact groupoid with open range map does not always admit a Haar system. It then is shown how to construct a Haar system if the stability groupoid and the quotient by the stability groupoid both admit one.

Operator Algebras · Mathematics 2017-11-03 Anton Deitmar

In 1985 S.~Saeki and K.~Stromberg published the following question: {\it Does every infinite compact group have a subgroup which is not Haar measurable?} An affirmative answer is given for all compact groups with the exception of some…

Group Theory · Mathematics 2014-06-27 Salvador Hernández , Karl H. Hofmann , Sidney A. Morris

We characterize the situation of having many normal measures on a measurable cardinal. We show the plausibility of having many normal measures on each compact cardinal.

Logic · Mathematics 2016-02-10 Shimon Garti