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1h
reviewed Delete Proof inequality using Lagrange Multipliers
5h
revised Prove that a complete field defines a partition of a set
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6h
comment Does meet of two partitions of a set always exist?
Yes. Partitions form a complete lattice.
6h
revised Does meet of two partitions of a set always exist?
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7h
revised Decomposition of a Set System into Distributive Lattices
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8h
awarded  Nice Answer
10h
comment After switching a lamp on and off infinitely many times in one minute, is it on or off?
Actually, there is a sense of odd and even for ordinals. And $\omega$ is even. This is not the same question though, since it would only matter if the sequence converges, then you can say that the $\omega$-th state is the limit of the previous steps. We expect "everything" to be continuous, since discrete [e.g. finite] processes are continuous. But this is of course not true.
10h
answered Why do we know that Gödel sentences are true in the standard model of set theory, but do not know if the continuum hypothesis is?
11h
revised An injection from R × {0, 1} to R
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11h
comment Why do we know that Gödel sentences are true in the standard model of set theory, but do not know if the continuum hypothesis is?
What is the standard model of $\sf ZFC$?
20h
comment After switching a lamp on and off infinitely many times in one minute, is it on or off?
This is a cute comment, but it's not an answer.
20h
comment Good resources for studying independence proofs
I've clarified the point about Boolean valued approach vs. forcing. Halbeisen's book doesn't have a lot of preliminary requirements actually. It's quite thorough and good. It doesn't have exercises, though. As for Kunen, I leafed through the new book, and I read bits and pieces of the old one. I can't say that I'm a huge fan, and at times I feel drowning with formalities and notations. Perhaps there is better motivation given, which is in the parts I skipped. It's probably better than Jech as a whole, but I think Halbeisen is just great.
20h
revised Good resources for studying independence proofs
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21h
revised Prove that $\{(x,y)\mid xy>0\}$ is open
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22h
revised Good resources for studying independence proofs
added 593 characters in body
22h
revised Good resources for studying independence proofs
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22h
answered Good resources for studying independence proofs
22h
revised An open interval as a union of closed intervals
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22h
comment General notions of basis
I imagine a minimal [with respect to inclusion] set $A$ such that the closure of $A$ is the entire model; or alternatively, a maximal set of elements such that no element is in the substructure (or "sufficiently elementary submodel" perhaps) generated by the other elements of the set. But those are idle speculations.
1d
comment After switching a lamp on and off infinitely many times in one minute, is it on or off?
@achillehui: There's also $\frac1{\sqrt2}$ chance that the lamp is broken; and another $\frac1{\sqrt3}$ that it got stolen. :-)