Re: Aleph question



In article <1147123641.709454.131050@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Guy L. <gihyunlee@xxxxxxxxx> wrote:

Please learn to quote.

http://groups.google.com/support/bin/answer.py?answer=14213&topic=250

Would this solution also work:

No since, cofinality of 2^aleph_0 is uncountable by Konig's Thm but
cofinality of aleph_(w1*5+w) = aleph_(w1*5+w),

Do you know what "cofinality" means? The cofinality of aleph_{w1*5+w}
is not aleph_{w1*5+w}, it is in fact omega: the subset
{aleph_{w1*5+i} | i in omega} is cofinal in aleph_{w1*5+w}, and since
infinite cardinals are all limit ordinals, it cannot be any smaller
than omega.

therefore 2^aleph_0 cannot equal aleph_(w1*5+w)

Yes. 2^{aleph_0} cannot be a cardinal with cofinality omega. There are
other conditions that restrict possible values of 2^{aleph_0}, as I
recall (though I could be wrong), but this is the easiest one.

--
======================================================================
"It's not denial. I'm just very selective about
what I accept as reality."
--- Calvin ("Calvin and Hobbes")
======================================================================

Arturo Magidin
magidin@xxxxxxxxxxxxxxxxx

.



Relevant Pages

  • Re: Aleph question
    ... I am new to these groups things so sorry about the non-quoting. ... Arturo Magidin wrote: ... infinite cardinals are all limit ordinals, ... 2^cannot be a cardinal with cofinality omega. ...
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  • Re: Aleph question
    ... I am new to these groups things so sorry about the non-quoting. ... Arturo Magidin wrote: ... infinite cardinals are all limit ordinals, ... 2^cannot be a cardinal with cofinality omega. ...
    (sci.math)
  • Re: Aleph question
    ... I am new to these groups things so sorry about the non-quoting. ... Arturo Magidin wrote: ... infinite cardinals are all limit ordinals, ... 2^cannot be a cardinal with cofinality omega. ...
    (sci.math)
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