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We define and discuss G-formality for certain spaces endowed with an action by a compact Lie group. This concept is essentially formality of the Borel construction of the space in a category of commutative differential graded algebras over…

Algebraic Topology · Mathematics 2007-05-23 Steven Lillywhite

Let $G$ be a semisimple Lie group acting on a space $X$, let $\mu$ be a compactly supported measure on $G$, and let $A$ be a strongly irreducible linear cocycle over the action of $G$. We then have a random walk on $X$, and let $T$ be the…

Dynamical Systems · Mathematics 2019-01-09 Alex Eskin , Carlos Matheus

Let L\subset V=\bR^{k,l} be a maximally isotropic subspace. It is shown that any simply connected Lie group with a bi-invariant flat pseudo-Riemannian metric of signature (k,l) is 2-step nilpotent and is defined by an element \eta \in…

Differential Geometry · Mathematics 2009-08-03 Vicente Cortés , Lars Schäfer

We construct invariant complex product (hyperparacomplex, indefinite quaternion) structures on the manifolds underlying the real noncompact simple Lie groups $SL(2m-1,\RR)$, $SU(m,m-1)$ and $SL(2m-1,\CC)^\RR$. We show that on the last two…

Differential Geometry · Mathematics 2007-05-23 Stefan Ivanov , Vasil Tsanov

This is a survey on left invariant semi-Riemannian metrics on compact Lie groups.

Differential Geometry · Mathematics 2025-05-19 Abdelghani Zeghib

In this work we introduce a criterion for testing general covariance in effective quantum gravity theories. It adapts the analysis of invariance under general spacetime diffeomorphisms of the Einstein-Hilbert action to the case of effective…

General Relativity and Quantum Cosmology · Physics 2025-05-12 Juan Carlos Del Águila , Hugo A. Morales

We show that a left invariant metric on a compact Lie group $G$ which is obtained by stretching a biinvariant metric in the direction of a subalgebra $\h$ of $\g$ always has some negative sectional curvature, unless the semi-simple part of…

Differential Geometry · Mathematics 2007-05-23 Lorenz J. Schwachhoefer

Let $M=G/K$ be a generalized flag manifold, that is the adjoint orbit of a compact semisimple Lie group $G$. We use the variational approach to find invariant Einstein metrics for all flag manifolds with two isotropy summands. We also…

Differential Geometry · Mathematics 2019-11-25 Andreas Arvanitoyeorgos , Ioannis Chrysikos

Haar measure is a fundamental structure in harmonic analysis on locally compact groups. Its existence reflects the compatibility between topology and the associative algebraic structure of groups. In this paper we propose a framework for…

Group Theory · Mathematics 2026-03-12 Takao Inoué

We introduce the construction of induced corepresentations in the setting of locally compact quantum groups and prove that the resulting induced corepresentations are unitary under some mild integrability condition. We also establish a…

Operator Algebras · Mathematics 2007-05-23 Johan Kustermans

In loop quantum gravity in the connection representation, the quantum configuration space $\bar{\mathcal{A}/\mathcal{G}}$, which is a compact space, is much larger than the classical configuration space $\mathcal{A}/% \mathcal{G}$ of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Andreas Doering , Hans F. de Groote

Let $G$ be $\text{SO}^\circ(n,1)$ for $n \geq 3$ and consider a lattice $\Gamma < G$. Given a standard Borel probability $\Gamma$-space $(\Omega,\mu)$, consider a measurable cocycle $\sigma:\Gamma \times \Omega \rightarrow…

Dynamical Systems · Mathematics 2023-12-11 Alessio Savini

For a closed locally symmetric space M=\Gamma\G/K and a representation of G we consider the push-forward of the fundamental class in the homology of the linear group and a related invariant in algebraic K-theory. We discuss the…

Geometric Topology · Mathematics 2014-10-01 Thilo Kuessner

In this paper we show that for every congruent monotileable amenable group $G$ and for every metrizable Choquet simplex $K$, there exists a minimal $G$-subshift, which is free on a full measure set, whose set of invariant probability…

Dynamical Systems · Mathematics 2017-09-26 Paulina Cecchi , María Isabel Cortez

Given any non-compact real simple Lie group G of inner type and even dimension, we prove the existence of an invariant complex structure J and a Hermitian balanced metric with vanishing Chern scalar curvature on G and on any compact…

Differential Geometry · Mathematics 2021-06-29 Federico Giusti , Fabio Podestà

Let $LG$ be the loop group of a compact, connected Lie group $G$. We show that the tangent bundle of any proper Hamiltonian $LG$-space $\mathcal{M}$ has a natural completion $\overline{T}\mathcal{M}$ to a strongly symplectic…

Symplectic Geometry · Mathematics 2017-06-26 Yiannis Loizides , Eckhard Meinrenken , Yanli Song

This is the second paper concerning gauge-invariant coherent states for Loop Quantum Gravity. Here, we deal with the gauge group SU(2), this being a significant complication compared to the abelian U(1) case encountered in the previous…

General Relativity and Quantum Cosmology · Physics 2009-02-12 Benjamin Bahr , Thomas Thiemann

The filtration on the infinite symmetric product of spheres by the number of factors provides a sequence of spectra between the sphere spectrum and the integral Eilenberg-Mac Lane spectrum. This filtration has received a lot of attention…

Algebraic Topology · Mathematics 2017-04-03 Stefan Schwede

Invariance and equivariance to geometrical transformations have proven to be very useful inductive biases when training (convolutional) neural network models, especially in the low-data regime. Much work has focused on the case where the…

Machine Learning · Computer Science 2024-07-11 Mircea Mironenco , Patrick Forré

Given an extension $0\to V\to G\to Q\to1$ of locally compact groups, with $V$ abelian, and a compatible essentially bijective $1$-cocycle $\eta\colon Q\to\hat V$, we define a dual unitary $2$-cocycle on $G$ and show that the associated…

Operator Algebras · Mathematics 2023-12-04 Pierre Bieliavsky , Victor Gayral , Sergey Neshveyev , Lars Tuset