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Q: Set Theory Proof - Need no later than Noon PST May 13, 2005 ... or not at all. ( No Answer,   1 Comment )
Question  
Subject: Set Theory Proof - Need no later than Noon PST May 13, 2005 ... or not at all.
Category: Miscellaneous
Asked by: thecuriousone-ga
List Price: $2.00
Posted: 12 May 2005 21:06 PDT
Expires: 13 May 2005 01:13 PDT
Question ID: 521161
Assuming the Axiom of Choice (AC) you can show that aleph_1 is not a
countable union of countable sets and, further, that you need SOME
choice (namely Countable Choice (AC_w)). Show in ZF (without any
choice) that aleph_2 is not a countable union of countable sets.
[Note: The following hint may help: Suppose for contradiction that
aleph_2 is a countable union of contable sets. Let alpha_n be the
ordertype of X_n and let alpha be the countable union of alpha_n.
Violate the fact that aleph_2 is a cardinal.]
Answer  
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Comments  
Subject: Re: Set Theory Proof - Need no later than Noon PST May 13, 2005 ... or not at all.
From: politicalguru-ga on 13 May 2005 00:07 PDT
 
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