Q-points, selective ultrafilters, and idempotents, with an application to choiceless set theory

David Fernández-Bretón, Jareb Navarro-Castillo, Jesús A. Soria-Rojas

We study ultrafilters from the perspective of the algebra in the Čech-Stone compactification of the natural numbers, and idempotent elements therein. The first two results that we…