29,292 reputation
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bio website dorais.org
location Hanover, NH
age
visits member for 5 years, 2 months
seen 39 mins ago

I like math and a few other things...


2d
revised Notion of strongness in cut rule
latexified
2d
comment Adding a real with infinite conditions
@Asaf The generalized Cohen forcing and generalized Silver forcing were introduced by Serge Grigorieff Combinatorics on ideals and forcing, Ann. Math. Logic 3 (1971), 363-394; MR0297560.
Jan
25
comment Recent trends in effective analysis
@JasonRute This is a pretty good answer. Maybe there are a few more details to add, but it's a really good summary of the current state of affairs. Why not post it as an answer?
Jan
23
comment On whether a formula of KP is $\Pi_3$
Do you mean $\Pi^0_3$ and $\Delta^0_1$?
Jan
21
comment Krein Milman theorem without the axiom of choice
There is a quantifier error in the "assertion". The assertion (*) in the paper has an implicit universal quantifier.
Jan
20
revised Does k(X) have a k-basis for every set X, without AC?
fixed small typos
Jan
20
awarded  Good Answer
Jan
15
comment The 'class version' of almost disjoint sets: can it fail?
I feel like it's been a while since we last posted almost simultaneous and essentially identical answers... Cheers!
Jan
15
answered The 'class version' of almost disjoint sets: can it fail?
Jan
14
comment Does k(X) have a k-basis for every set X, without AC?
@JeremyRickard: The unusual feature of Matt's definition is that vectors don't necessarily have a unique representation as an ordered linear combination of basis elements where all coefficients are nonzero. The usual unordered definition (see Emil's first comment) does have the expected uniqueness property.
Jan
13
comment Does k(X) have a k-basis for every set X, without AC?
Matt, you need to argue that the outcome of the decision is the same regardless of how the finite sums are ordered. Otherwise, you are choosing such an ordering for each pair $x,y$!
Jan
7
revised What is known about global well ordering of classes in Gödel-Bernays?
added 174 characters in body
Jan
7
revised What is known about global well ordering of classes in Gödel-Bernays?
edited title
Jan
7
comment A new cardinality living in every forcing extension?
Yeah, that's the "half-baked" part. The thing is that with SVC you can force AC for reasons totally unrelated to the "generic cardinal" and that seems like an issue. I haven't thought this through much so I'm not even convincing myself with this idea but it's not outright ridiculous...
Jan
7
comment A new cardinality living in every forcing extension?
This is just a "half-baked" thought: if $V$ satisfies SVC then one could force AC and that would make the generic cardinality "uninteresting". So, I guess, if there is such a thing then AC must fail "really badly" in $V$.
Dec
29
revised The Set-Theoretic Multiverse and Joint Embeddings
edited body
Dec
29
revised The Set-Theoretic Multiverse and Joint Embeddings
clarification about compatibility
Dec
29
answered The Set-Theoretic Multiverse and Joint Embeddings
Dec
22
comment Is it consistent that $\frak{d} < 2^{\aleph_0}$?
See the reference to Hechler in this answer: mathoverflow.net/a/29626
Dec
22
comment A question regarding $ZFC^{-}$
In that case, the powerset axiom is really hard to beat!