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Search options questions only not deleted user 11115
26 votes
1 answer
1k views

categorical characterization of large cardinals

Question 1. Is there a categorical representation of Kunen's inconsistency result? Question 2. Is there a categorical characterization of very large cardinals (in particular for strong and supercomp …
Mohammad Golshani's user avatar
21 votes
2 answers
2k views

Philosophical arguments in defense (or against) large cardinals

The question is essentially what is asked in the title. I split it into two parts (A) (Arguments supporting the existence of large cardinals) What are the main philosophical arguments in defense o …
19 votes
2 answers
2k views

Woodin's unpublished proof of the global failure of GCH

An unpublished result of Woodin says the following: Theorem. Assuming the existence of large cardinals, it is consistent that $\forall \lambda, 2^{\lambda}=\lambda^{++}.$ In the paper "The generaliz …
Mohammad Golshani's user avatar
17 votes
0 answers
903 views

Souslin trees and weakly compact cardinals

In Souslin trees on the first inaccessible cardinal it is asked if it is consistent that there are no $\kappa-$Souslin trees at the least inaccessible cardinal $\kappa$. In this question I would like …
Mohammad Golshani's user avatar
16 votes
0 answers
768 views

Ideas behind Gitik's solution of PCF conjecture

Recently Moti Gitik has refuted Shelah's PCF conjecture (see Short extenders forcings II ) by proving the following theorem: Theorem. Assuming the consistency of infinitely many strong cardinals, one …
Mohammad Golshani's user avatar
15 votes
1 answer
406 views

Consistency strength of $\aleph_2$-Souslin hypothesis

Question 1. What is known about the consistency strength of $\aleph_2$-Souslin hypothesis? Question 2. What is known about the consistency strength of having both $\aleph_2$-Souslin hypotheis and $\a …
Mohammad Golshani's user avatar
14 votes
0 answers
348 views

The failure of GCH al $\aleph_\omega$ by nice forcing

There are several ways to force $GCH$ below $\aleph_\omega$ and $2^{\aleph_\omega}> \aleph_{\omega+1},$ say: 1) The Gitik-Magidor's extender based forcing, see Prikry type Forcings. 2) Woodin's meth …
Mohammad Golshani's user avatar
14 votes
1 answer
717 views

The axiom $I_0$ in the absence of $AC$

It is well-known that if $AC$ holds and if $j: L(V_{\lambda+1}) \to L(V_{\lambda+1})$ is a non-trivial elementary embedding with $crit(j) < \lambda,$ then $\lambda$ has countable cofinality (and in fa …
Mohammad Golshani's user avatar
14 votes
3 answers
1k views

Questions about $\aleph_1-$closed forcing notions

"Foreman`s maximality principle" states that every non-trivial forcing notion either adds a real or collapses some cardinals. This principle has many consequences including: 1) $GCH$ fails everywhere …
Mohammad Golshani's user avatar
13 votes
2 answers
1k views

Failure of diamond at large cardinals

What is known about the failure of $\Diamond_{\kappa}$ (diamond at $\kappa$) for $\kappa$ (the least) inaccessible, (the least) Mahlo and (the least) weakly compact. Remark. The problem of forcing t …
Mohammad Golshani's user avatar
13 votes
1 answer
756 views

Changing cofinalities above supercompact cardinals

Question. Suppose $\kappa$ is a supercompact cardinal and $\lambda > \kappa$ is measurable (or even larger large cardinal if necessary). Is there a set generic extension of the universe in which $\ka …
Mohammad Golshani's user avatar
12 votes
3 answers
1k views

Necessary use of large cardinals in mathematics [duplicate]

There are some statements, whose consistency (or the consistency of their negation) require the existence of large cardinals (in the sense that if the statement (or its negation) is consistent, then i …
12 votes
2 answers
993 views

Kunen's inconsistency result

A well-known result of Kunen says that there is no non-trivial elementary embedding $j: V \rightarrow V.$ There are several proofs of this theorem (see Kanamori, The higher infinite). I wonder to know …
Mohammad Golshani's user avatar
12 votes
2 answers
1k views

Questions about Prikry forcing and Cohen forcing

I have some questions. The first one is about the product of Prikry's forcing. Let $\kappa$ be a measurable cardinal, $U_1, U_2$ be normal measures on $\kappa$ and let $\mathbb{P}_{U_1}, \mathbb{ …
Mohammad Golshani's user avatar
12 votes
0 answers
372 views

Singular Jonsson cardinals

Is the following consistent? $(*)$: There exists a singular cardinal $\kappa$ such that : (1) $\kappa$ is a Jonsson cardinal, (2) $\kappa$ is not a fixed point of the $\aleph-$function, i.e., $\kappa …
Mohammad Golshani's user avatar

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