In mathematics, a locally compact group is a topological group G for which the underlying topology is locally compact and Hausdorff. Locally compact groups are important because many examples of groups that arise throughout mathematics are locally compact and such groups have a natural measure called the Haar measure. This allows one to define integrals of Borel measurable functions on G so that standard analysis notions such as the Fourier transform and spaces can be generalized.
Many of the results of finite group representation theory are proved by averaging over the group. For compact groups, modifications of these proofs yields similar results by averaging with respect to the normalized Haar integral. In the general locally compact setting, such techniques need not hold. The resulting theory is a central part of harmonic analysis. The representation theory for locally compact abelian groups is described by Pontryagin duality.
Any compact group is locally compact.
In particular the circle group T of complex numbers of unit modulus under multiplication is compact, and therefore locally compact. The circle group historically served as the first topologically nontrivial group to also have the property of local compactness, and as such motivated the search for the more general theory, presented here.
Any discrete group is locally compact. The theory of locally compact groups therefore encompasses the theory of ordinary groups since any group can be given the discrete topology.
Lie groups, which are locally Euclidean, are all locally compact groups.
A Hausdorff topological vector space is locally compact if and only if it is finite-dimensional.
The additive group of rational numbers Q is not locally compact if given the relative topology as a subset of the real numbers. It is locally compact if given the discrete topology.
The additive group of p-adic numbers Qp is locally compact for any prime number p.
By homogeneity, local compactness of the underlying space for a topological group need only be checked at the identity.
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This course is an introduction to the theory of Riemann surfaces. Riemann surfaces naturally appear is mathematics in many different ways: as a result of analytic continuation, as quotients of complex
We establish new results on the weak containment of quasi-regular and Koopman representations of a second countable locally compact group GG associated with nonsingular GG-spaces. We deduce that any two boundary representations of a hyperbolic locally ...
Le cinquième problème de Hilbert fait partie de la liste des vingt-trois problèmes posés par David Hilbert en 1900, et concerne la caractérisation des groupes de Lie. Il s'agissait (dans un langage moderne et en interprétant la question, puisqu'à l'époque la notion précise de variété différentielle n'existait pas) de démontrer que dans la définition d'un groupe de Lie, la condition de différentiabilité est redondante.
En mathématiques, un nombre réel est un nombre qui peut être représenté par une partie entière et une liste finie ou infinie de décimales. Cette définition s'applique donc aux nombres rationnels, dont les décimales se répètent de façon périodique à partir d'un certain rang, mais aussi à d'autres nombres dits irrationnels, tels que la racine carrée de 2, π et e.
In mathematics, a topological group G is called a discrete group if there is no limit point in it (i.e., for each element in G, there is a neighborhood which only contains that element). Equivalently, the group G is discrete if and only if its identity is isolated. A subgroup H of a topological group G is a discrete subgroup if H is discrete when endowed with the subspace topology from G. In other words there is a neighbourhood of the identity in G containing no other element of H.
We present a self-contained proof of the following famous extension theorem due to Carl Herz. A closed subgroup H of a locally compact group G is a set of p-synthesis in G if and only if, for every u is an element of A(p)(H) boolean AND C-00(H) and for eve ...
We study a fixed point property for linear actions of discrete groups on weakly complete convex proper cones in locally convex topological vector spaces. We search to understand the class of discrete groups which enjoys this property and we try to generali ...