English

An example of a rigid $\kappa$-superuniversal metric space

General Topology 2014-07-15 v1

Abstract

For a cardinal κ>ω\kappa > \omega a metric space XX is called to be κ\kappa-superuniversal whenever for every metric space YY with Y<κ|Y| < \kappa every partial isometry from a subset of YY into XX can be extended over the whole space YY. Examples of such spaces were given by Hechler [1] and Kat\v{e}tov [2]. In particular, Kat\v{e}tov showed that if ω<κ=κ<κ\omega < \kappa = \kappa^{< \kappa}, then there exists a κ\kappa-superuniversal KK which is moreover κ\kappa-homogeneous, i.e. every isometry of a subspace YKY\subseteq K with Y<κ|Y|<\kappa can be extended to an isometry of the whole KK. In connection of this W. Kubi\'s suggested that there should also exist a κ\kappa-superuniversal space that is not κ\kappa-homogeneous. In this paper there is shown that for every cardinal κ\kappa there exists a κ\kappa-superuniversal space which is rigid, i.e. has exactly one isometry, namely the identity. The construction involves an amalgamation-like property of a family of metric spaces.

Keywords

Cite

@article{arxiv.1407.3767,
  title  = {An example of a rigid $\kappa$-superuniversal metric space},
  author = {Wojciech Bielas},
  journal= {arXiv preprint arXiv:1407.3767},
  year   = {2014}
}