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first-order and higher-order logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, philosophical logic, modal logic, completeness, Gödel incompleteness, decidability, undecidability, theories of truth, truth revision, consistency.

6 votes
1 answer
215 views

On the number of complete Boolean algebras

In their 1972 paper On the number of complete Boolean algebras Monk and Solovay showed that if $\lambda$ is an infinite cardinal, then there are $2^{2^\lambda}$ many isomorphism types of complete Boo …
Mohammad Golshani's user avatar
5 votes
0 answers
191 views

Product of nice proper forcing notions

Question Are there forcing notions $P$ and $Q$ such that $P$ is proper and $\aleph_2$-cc, $Q$ is proper and satisfies the $\aleph_2$-pic (pic=properness isomorphism condition) such that $P \times Q$ i …
Mohammad Golshani's user avatar
12 votes
2 answers
906 views

Bernstein's proof of the continuum hypothesis

In the paper The Continuumproblem, Felix Bernstein introduces a new axiom and uses it to conclude the continuum hypothesis. (1) As the paper is relatively old and the writing style is somehow informal …
Mohammad Golshani's user avatar
15 votes
0 answers
1k views

Condensed mathematics and independence results

I recently saw a paper on ``condensed mathematics'', in which I found the following quote interesting (see Condensed Mathematics: The internal Hom of condensed sets and condensed abelian groups and a …
Mohammad Golshani's user avatar
4 votes
0 answers
202 views

PFA for cardinal preserving forcing notions and the CH

Let $FA_{\aleph_1}$(cardinal preserving proper forcings) be the forcing axiom: if $\mathbb{P}$ is a cardinal preserving proper forcing notion and $(D_\xi)_{\xi<\omega_1}$ are dense subsets of $\mathb …
Mohammad Golshani's user avatar
12 votes
2 answers
580 views

Forcing notions adding minimal reals

I am looking for a comprehensive list of known forcing notions which add a minimal real into the ground model. I know some of them like the Sacks forcing, or the Judah-Shelah's example of a c.c.c. for …
Mohammad Golshani's user avatar
13 votes
0 answers
696 views

Applications of Set theory vs. model theory in mathematics

I have a question that has occupied my mind for some time. Let's first consider applications of set theory and model theory in mathematics. Major applications of set theory are in topology, Banach spa …
Mohammad Golshani's user avatar
8 votes
0 answers
182 views

Topological Vaught's conjecture for special theories

As is know, Vaught's conjecture is a special case of topological Vaught's conjecture. On the other hand, the Vaught's conjecture is true for the following theories: 1- $\omega$-stable theories (Shel …
Mohammad Golshani's user avatar
11 votes
2 answers
705 views

ZFC applications of Shelah's creature forcing

Shelah's creature forcing is a very powerful method, with wide range of applications. The method also has some applications in ZFC, let's quote a few of them that I am aware of: (1) In A partition the …
Mohammad Golshani's user avatar
14 votes
0 answers
498 views

The Ax-Kochen isomorphism theorem and the continuum hypothesis

Let's recall that: (1): The Ax-Kochen principle says that if $\mathcal{U}$ is a non-principal ultrafilter over prime numbers, then $\prod_{\mathbb{U}} \mathbb{F}_p((t)) \equiv \prod_{\mathbb{U}} \mat …
Mohammad Golshani's user avatar
7 votes
1 answer
326 views

Effective set= ordinal definable set

I just today realized that the concept of ordinal definability is defined in a different way by vopenka-Balcar-Hajek ``The notion of effective sets and a new proof of the consistency of the axiom of …
Mohammad Golshani's user avatar
6 votes
0 answers
315 views

measure of generic reals in forcing extensions

It is well-known that if $V[G]$ is a generic extension by adding a Cohen real, then the set $\{r \in V[G]: r$ is Cohen generic over $V\}$ has measure zero. On the other hand, if $V[G]$ is a generic …
Mohammad Golshani's user avatar
14 votes
0 answers
402 views

O-minimality and forcing

It is well-known that the structure $(\mathbb{R}, +, \cdot, <, 0, 1)$ is an o-minimal structure and hence the set of integers $\mathbb{Z}$ is not definable in it. In an ongoing project with Will Bria …
Mohammad Golshani's user avatar
2 votes
1 answer
274 views

A variant of Radin forcing

Suppose $\kappa$ is a large cardinal (strong cardinal seems to be enough). Is there a forcing notion $\mathbb{R}$ with the following properties: $(1)$ Forcing with $\mathbb{R}$ adds a club $C$ into $ …
Mohammad Golshani's user avatar
10 votes
2 answers
1k views

Examples of set theory problems which are solved using methods outside of logic

The question is essentially the one in the title. Question. What are some examples of (major) problems in set theory which are solved using techniques outside of mathematical logic?
Mohammad Golshani's user avatar

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