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2d

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A question about Borel sets on the unit interval
Yes, thanks. And thanks for the reference in your answer. 
2d

revised 
A question about Borel sets on the unit interval
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2d

accepted  A question about Borel sets on the unit interval 
2d

asked  A question about Borel sets on the unit interval 
Jan
26 
accepted  Why hasn't mereology succeeded as an alternative to set theory? 
Jan
26 
comment 
Why hasn't mereology succeeded as an alternative to set theory?
That a decidable theory cannot be foundational is a beautiful argument. It reveals the richness one gets from incompleteness. 
Jul
18 
comment 
riemann mapping theorem for skewfields of quaternions and beyond
Please check the following paper on the subject: C.A. Deavours (1973) "The Quaternion Calculus", American Mathematical Monthly 80:995–1008. 
Apr
12 
awarded  Enlightened 
Apr
12 
awarded  Nice Answer 
Feb
14 
awarded  Yearling 
Jan
12 
comment 
A question regarding the HahnBanach theorem
It's clear that such a measure must take values within $0$ and $1$, but in order to even state countable additivity you would need $B$ to have countable joins and meets, which is not necessarily going to happen. Regarding $WKL_0$, you need to specify which base theory and which statement of HahnBanach theorem you are considering. $ZF$ is too strong since it proves Weak König's lemma, and the general formulation of HahnBanach theorem as in the above equivalence involves arbitrary vector spaces not necessarily definable in second order arithmetic. 
Jan
9 
answered  A question regarding the HahnBanach theorem 
Dec
7 
comment 
What are the current views on consistency of Reinhardt cardinals without AC?
...But it is conceivable that a large cardinal hierarchy could be mirrored in an intuitionistic setting where more notions of large cardinals can be defined without inconsistency (they will have to be nonclassical though). 
Dec
7 
comment 
What are the current views on consistency of Reinhardt cardinals without AC?
This is just speculative, but even if some large cardinals are found to be inconsistent with ZF, there could be weaker set theories where appropriate versions are consistent. I'm thinking more precisely of Aczel's constructive set theory CZF, based on intuitionistic logic, over which appropriate notions of regular, inaccessible and even Mahlo cardinals are defined (see "Inaccessibility in constructive set theories and type theories" by RathjenGrifforPalmgren). In this case, the addition of AC turns the theory in just ZFC plus the usual notions...(cont.) 
Dec
6 
comment 
$\zeta(0)$ and the cotangent function
Given the fact that what you end up explaining why the series, considered as a Laurent series, predicts also the values of $\zeta$ at the negative even numbers, I think this proof is as simple as it reasonably can be expected to be. This because you are forced to consider the analytic continuation of $\zeta$ to the left half plane, not just to the critical strip, so it's reasonable that the functional equation is invoked. 
Nov
5 
comment 
Mysterious quotes (at least for me)
There is a very particular way in which those quotes make sense to me, but I'm afraid is not a mathematical way so I can't really answer :) 
Oct
16 
revised 
Is it possible to formulate the axiom of choice as the existence of a survival strategy?
added 1981 characters in body 
Oct
15 
answered  Is it possible to formulate the axiom of choice as the existence of a survival strategy? 
Sep
25 
comment 
An interpretation of notCon(PA)
Careful! All that the the 2nd incompleteness theorem tells you is that $Con(PA)$ is unprovable, not that it is independent, and this provided you already accept the consistency of PA. If you apply that theorem to your theory $PA^+$ instead, you can only conclude that $Con(PA^+)$ is unprovable in $PA^+$, because in fact $\neg Con(PA^+)$ is actually provable there. 
Sep
24 
awarded  Autobiographer 