IM PAN
INSTITUTE OF MATHEMATICS · POLISH ACADEMY OF SCIENCES
FUNDAMENTA
MATHEMATICAE
ISSN: 0016-2736(p) 1730-6329(e)
 

Compactifications of N and Polishable subgroups of S
Todor Tsankov1
Fund. Math. 189 (2006), 269-284

Abstract: 
We study homeomorphism groups of metrizable compactifications of
$\mathbb{N}$. All of those groups can be represented as almost
zero-dimensional Polishable subgroups of the group $S_\infty$.
As a corollary, we show that all Polish groups are continuous
homomorphic images of almost zero-dimensional Polishable
subgroups of $S_\infty$. We prove a sufficient condition for
these groups to be one-dimensional and also study their
descriptive complexity. In the last section we associate with
every Polishable ideal on $\mathbb{N}$ a certain Polishable
subgroup of $S_\infty$ which shares its topological dimension
and descriptive complexity.


MSC (2000): Primary 54H05, 54H15; Secondary 54F50.
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  1. Department of Mathematics 253-37
    California Institute of Technology
    Pasadena, CA 91125, U.S.A.