Effective cardinals in the nonstandard universe
arXiv:math/0512054 · doi:10.1142/6255
Abstract
We study the structure of effective cardinals in the nonstandard set universe of Hrbacek set theory HST. Some results resemble those known in descriptive set theory in the domain of Borel reducibility of equivalence relations.
Support of DFG grant 436 RUS 17/68/05 and RFBR 03-01-00757 acknowledged