The Ultrapower Axiom UA and the number of normal measures over χ1 and χ2
A. W. Apter
We show that assuming the consistency of certain large cardinals (namely a supercompact cardinal with a
measurable cardinal above it of the appropriate Mitchell order) together with the Ultrapower Axiom UA introduced by
Goldberg in [3], it is possible to force and construct choiceless universes
of ZF in which the first two uncountable cardinals χ1 and χ2 are both measurable
and carry certain fixed numbers of normal measures.
Specifically, in the models constructed, χ1 will carry exactly one normal
measure, namely μω ={ x ⊆ χ1 | x contains a club set }, and χ2
will carry exactly τ normal measures, where τ = χn for n = 0,1,2 or
τ = n for n ≥ 1 an integer (so in particular, τ ≤ χ2 is any nonzero finite or infinite cardinal).
This complements the results of [1] in which τ ≥ χ3 and contrasts with the well-known facts that assuming
AD + DC, χ1 is measurable and carries exactly one normal measure, and χ2 is measurable and carries exactly two normal measures.
Tbilisi Mathematical Journal, Vol. 14(1) (2021), pp. 49-53
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