Hostname: page-component-84b7d79bbc-g78kv Total loading time: 0 Render date: 2024-07-25T17:24:55.084Z Has data issue: false hasContentIssue false

Closed Left Ideal Decompositions of U(G)

Published online by Cambridge University Press:  20 November 2018

Yevhen Zelenyuk*
Affiliation:
School of Mathematics, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa e-mail: yevhen.zelenyuk@wits.ac.za
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Let $G$ be an infinite discrete group and let $\beta G$ be the Stone-Čech compactification of $G$. We take the points of $\beta G$ to be the ultrafilters on $G$, identifying the principal ultrafilters with the points of $G$. The set $U\left( G \right)$ of uniform ultrafilters on $G$ is a closed two-sided ideal of $\beta G$. For every $p\,\in \,U\left( G \right)$, define ${{I}_{p}}\,\subseteq \,\beta G$ by ${{I}_{p}}\,=\,{{\bigcap }_{A\in p}}\text{cl}\left( GU\left( A \right) \right)$, where $U\left( A \right)\,=\,\left\{ p\,\in \,U\left( G \right)\,:\,A\in \,p \right\}$. We show that if $\left| G \right|$ is a regular cardinal, then $\left\{ {{I}_{p}}\,:\,p\,\in \,U\left( G \right) \right\}$ is the finest decomposition of $U\left( G \right)$ into closed left ideals of $\beta G$ such that the corresponding quotient space of $U\left( G \right)$ is Hausdorff.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2013

References

[1] Davenport, D. and Hindman, N., A proof of van Douwen's right ideal theorem. Proc. Amer. Math. Soc. 113(1991), no. 2, 573580. Google Scholar
[2] Engelking, R., General topology. Sigma Series in Pure Mathematics, 6, Heldermann Verlag, Berlin, 1989.Google Scholar
[3] Hindman, N. and Strauss, D., Algebra in the Stone- ˇ Cech compactification. Theory and applications. de Gruyter Expositions in Mathematics, 27, Walter de Gruyter, Berlin, 1998.Google Scholar
[4] Filali, M. and Salmi, P., Slowly oscillating functions in semigroup compactifications and convolution algebras. J. Funct. Anal. 250(2007), no. 1, 144166. http://dx.doi.org/10.1016/j.jfa.2007.05.004 Google Scholar
[5] Protasov, I. V., Coronas of balleans. Topology Appl. 149(2005), no. 13. 149160. http://dx.doi.org/10.1016/j.topol.2004.09.005 Google Scholar