@article{Protasov_Slobodianiuk_2015, title={Ultrafilters on balleans}, volume={67}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/2102}, abstractNote={A ballean (equivalently, a coarse structure) is an asymptotic counterpart of a uniform space. We introduce three ultrafilter satellites of a ballean (namely, corona, companion, and corona companion), evaluate the basic cardinal invariants of the corona and characterize the subsets of balleans in terms of companions.}, number={12}, journal={Ukrains’kyi Matematychnyi Zhurnal}, author={Protasov, I. V. and Slobodianiuk, S. V.}, year={2015}, month={Dec.}, pages={1698-1706} }