Sergey A. Antonyan
Published 2009-05-15, updated 2012-08-31Version 2
Let X be a Hausdorff topological group and G a locally compact subgroup of X. We show that the natural action of G on X is proper in the sense of R. Palais. This is applied to prove that there exists a closed set F of X such that FG=X and the restriction of the quotient projection X -> X/G to F is a perfect map F -> X/G. This is a key result to prove that many topological properties (among them, paracompactness and normality) are transferred from X to ferred from X/G to X. Yet another application leads to the inequality dim X<= dim X/G + dim G for every paracompact group X and its locally compact subgroup G.
Comments: In the proof of Proposition 3.1 of the previous version there is a small gap. To correct the gap, at the end of the proof (now Proposition 3.2) one should just reference to a newly added Lemma 3.1 for the fact that Ux is a G-small set. Results unchanged. arXiv admin note: substantial text overlap with arXiv:1103.1407
Journal: Proc. AMS, vol. 138, no. 10 (2010), 3707-3716
Locally compact subgroup actions on topological groups
Extension properties of orbit spaces for proper actions revisited
Every topological group is a group retract of a minimal group
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