English

The weights of closed subgroups of a locally compact group

Group Theory 2012-01-19 v1 General Topology

Abstract

Let GG be an infinite locally compact group and \aleph a cardinal satisfying 0w(G)\aleph_0\le\aleph\le w(G) for the weight w(G)w(G) of GG. It is shown that there is a closed subgroup NN of GG with w(N)=w(N)=\aleph. Sample consequences are: (1) Every infinite compact group contains an infinite closed metric subgroup. (2) For a locally compact group GG and \aleph a cardinal satisfying 0\lw(G)\aleph_0\le\aleph\le \lw(G), where \lw(G)\lw(G) is the local weight of GG, there are either no infinite compact subgroups at all or there is a compact subgroup NN of GG with w(N)=w(N)=\aleph. (3) For an infinite abelian group GG there exists a properly ascending family of locally quasiconvex group topologies on GG, say, (τ)0\card(G)(\tau_\aleph)_{\aleph_0\le \aleph\le \card(G)}, such that (G,τ)m^G^(G,\tau_\aleph)\hat{\phantom{m}}\cong\hat G. Items (2) and (3) are shown in Section 5.

Keywords

Cite

@article{arxiv.1201.3814,
  title  = {The weights of closed subgroups of a locally compact group},
  author = {Salvador Hernández and Karl H. Hofmann and Sidney A. Morris},
  journal= {arXiv preprint arXiv:1201.3814},
  year   = {2012}
}