Geodesic
Ultracompanions of subsets of a group
Commentationes Mathematicae Universitatis Carolinae, Tome 55 (2014) no. 2, pp. 257-265.

Voir la notice de l'article provenant de la source Czech Digital Mathematics Library

Let $G$ be a group, $\beta G$ be the Stone-Čech compactification of $G$ endowed with the structure of a right topological semigroup and $G^*=\beta G\setminus G$. Given any subset $A$ of $G$ and $p\in G^*$, we define the $p$-companion $\Delta _p(A)= A^*\cap Gp$ of $A$, and characterize the subsets with finite and discrete ultracompanions.
Classification : 20F69, 22A15, 54D35
Keywords: Stone-Čech compactification; ultracompanion; sparse and discrete subsets of a group 
@article{CMUC_2014__55_2_a10,
     author = {Protasov, I. and Slobodianiuk, S.},
     title = {Ultracompanions of subsets of a group},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {257--265},
     publisher = {mathdoc},
     volume = {55},
     number = {2},
     year = {2014},
     mrnumber = {3193930},
     zbl = {06391542},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_2014__55_2_a10/}
}
TY  - JOUR
AU  - Protasov, I.
AU  - Slobodianiuk, S.
TI  - Ultracompanions of subsets of a group
JO  - Commentationes Mathematicae Universitatis Carolinae
PY  - 2014
SP  - 257
EP  - 265
VL  - 55
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/CMUC_2014__55_2_a10/
LA  - en
ID  - CMUC_2014__55_2_a10
ER  - 
%0 Journal Article
%A Protasov, I.
%A Slobodianiuk, S.
%T Ultracompanions of subsets of a group
%J Commentationes Mathematicae Universitatis Carolinae
%D 2014
%P 257-265
%V 55
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/CMUC_2014__55_2_a10/
%G en
%F CMUC_2014__55_2_a10
Protasov, I.; Slobodianiuk, S. Ultracompanions of subsets of a group. Commentationes Mathematicae Universitatis Carolinae, Tome 55 (2014) no. 2, pp. 257-265. http://geodesic.mathdoc.fr/item/CMUC_2014__55_2_a10/