Geodesic
The topological center of the semigroup of free ultrafilters
Matematičeskie zametki, Tome 63 (1998) no. 3, pp. 437-441.

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For any group $G$, it is proved that the topological center of the semigroup of free ultrafilters on the group $G$ is empty. 
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     title = {The topological center of the semigroup of free ultrafilters},
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I. V. Protasov. The topological center of the semigroup of free ultrafilters. Matematičeskie zametki, Tome 63 (1998) no. 3, pp. 437-441. http://geodesic.mathdoc.fr/item/MZM_1998_63_3_a14/

[1] Lau A., Pym J., “The topological centre of a compactification of a locally compact group”, Math. Z., 219 (1995), 567–579 | DOI | MR | Zbl

[2] Shelah S., Proper Forcing, Lecture Notes in Math., 940, Springer, Berlin, 1982 | Zbl

[3] Protasov I. V., “Tochki sovmestnoi nepreryvnosti polugruppy ultrafiltrov abelevoi gruppy”, Matem. sb., 187:2 (1996), 131–140 | MR | Zbl

[4] Blass A., Hindman N., “On strongly summable and union ultrafilters”, Trans. Amer. Math. Soc., 304:1 (1987), 83–99 | DOI | MR | Zbl