The spectrum of ultraproducts of finite cardinals for an ultrafilter

@article{Shelah2018TheSO,
title={The spectrum of ultraproducts of finite cardinals for an ultrafilter},
author={Saharon Shelah},
journal={Acta Mathematica Hungarica},
year={2018},
volume={155},
pages={201-220}
}

We complete the characterization of the possible spectrum of regular ultrafilters D on a set I, where the spectrum is the set of ultraproducts of (finite) cardinals modulo D which are infinite.

A combinatorial characterization of the class C is given that if D is a uniform ultrafilter on a cardinal κ and D is ${\aleph _1}$-complete or ${\theta_1} + {\theta _2} > {2^\kappa}.Expand

1. Sh:a Saharon Shelah. Classification theory and the number of nonisomorphic models, volume 92 of Studies in Logic and the Foundations of Mathematics. North-Holland Publishing Co., Amsterdam-New… Expand

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