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Apostolos
  • Member for 14 years
  • Last seen more than 2 years ago
  • Netherlands
26 votes
Accepted

Do sets, whose power sets have the same cardinality, have the same cardinality?

16 votes
Accepted

Prove 7 divides $15^n+6$ with mathematical induction

15 votes
Accepted

Prove that $\beta \rightarrow \neg \neg \beta$ is a theorem using standard axioms 1,2,3 and MP

14 votes
Accepted

Naive set theory question on "="

13 votes
Accepted

Proving that for infinite $\kappa$, $|[\kappa]^\lambda|=\kappa^\lambda$

12 votes
Accepted

An Exercise in Kunen (A Model for Foundation, Pairing,...)

11 votes
Accepted

Cardinality of the infinite sets

11 votes
Accepted

Conditions Equivalent to Injectivity

11 votes

Cofinality and its Consequences

10 votes
Accepted

Proof: Cartesian Product of Two Sets is a Set ZF

9 votes
Accepted

Logic, set theory, independence proofs, etc

9 votes

Does $k+\aleph_0=\mathfrak{c}$ imply $k=\mathfrak{c}$ without the Axiom of Choice?

9 votes

How do the separation axioms follow from the replacement axioms?

9 votes

How to prove that from "Every infinite cardinal satisfies $a^2=a$" we can prove that $b+c=bc$ for any two infinite cardinals $b,c$?

9 votes

Metalogic: Prove $\{\neg P_1 \to P_2\} \vdash (\neg P_2\to P_1)$ without using the Deduction Theorem

9 votes
Accepted

Example of a not recursively enumerable set $A \subseteq \mathbb{N}$

9 votes

Does $\mathsf{ZFC} + \neg\mathrm{Con}(\mathsf{ZFC})$ suffice as a foundations of mathematics?

7 votes
Accepted

How to remove constant symbols from a first-order theory?

7 votes

Why is cofinality important? And some help in proving absoluteness for $R(\kappa)$

7 votes
Accepted

Does a "backwards" choice function imply the Axiom of Choice?

7 votes
Accepted

Tarski-Vaught test for $\preceq$ reduction

7 votes
Accepted

Question about the order of a Stationary subset of $ \kappa$

7 votes
Accepted

proof that union of a sequence of countable sets is countable.

7 votes

Is Robinson Arithmetic complete and not-complete?

7 votes
Accepted

On the definition of weakly compact cardinals

6 votes

Finitely axiomatizable theories

6 votes
Accepted

With Choice, is any linearly ordered set well-ordered if no subset has order type $\omega^*$?

6 votes

Measurable cardinal existence condition

6 votes

Non-isomorphic atomless Boolean algebras

6 votes
Accepted

Show that an elementary equivalent structure of $\mathbb{R}$ and definable from points is Dedekind complete