The main results concern commutativity of Hewitt-Nachbin realcompactification or Dieudonné completion with products of topological groups. It is shown that for every topological group $G$ that is not Dieudonné complete one can find a Dieudonné complete group $H$ such that the Dieudonné completion of $G\times H$ is not a topological group containing $G\times H$ as a subgroup. Using Korovin's construction of $G_\delta$-dense orbits, we present some examples showing that some results on topological groups are not valid for semitopological groups.
@article{119232, author = {Aleksander V. Arhangel'skii and Miroslav Hu\v sek}, title = {Extensions of topological and semitopological groups and the product operation}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {42}, year = {2001}, pages = {173-186}, zbl = {1053.54043}, mrnumber = {1825381}, language = {en}, url = {http://dml.mathdoc.fr/item/119232} }
Arhangel'skii, Aleksander V.; Hušek, Miroslav. Extensions of topological and semitopological groups and the product operation. Commentationes Mathematicae Universitatis Carolinae, Tome 42 (2001) pp. 173-186. http://gdmltest.u-ga.fr/item/119232/
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