[FOM] Algebraic closure of Q
Thomas Forster
T.Forster at dpmms.cam.ac.uk
Tue May 16 04:11:17 EDT 2006
The way in which this question involves AC calls to mind a
related problem. It is known that if AC fails badly enough,
then the reals can be a union of countably many countable sets.
Can there be - again if AC fails badly enough - a countable
subgroup of the full symmetric group on the naturals - of
countable index? The point is that altho' the cosets of a
subgroup are always "pairwise equipollent", they are not
*uniformly* equipollent....
tf
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