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Arno's user avatar
Arno's user avatar
Arno
  • Member for 10 years, 4 months
  • Last seen this week
25 votes

Problem in an inductive proof of Brouwer's fixed point theorem.

24 votes

What inner monologue appears when you read Mathematical expressions?

17 votes
Accepted

A seemingly contradictory function - where's the issue?

12 votes

Do nonconstructive proofs of isomorphism exist?

9 votes
Accepted

Continuous bijection from non-compact set to compact set

9 votes

What does constructive mathematics say about limits?

8 votes
Accepted

Why is "Turing machine makes no left move" decidable?

8 votes
Accepted

How do I stop overcomplicating proofs?

8 votes

Does every ordinal have a well-defined "next" limit ordinal?

7 votes

Is there any uncountably infinite set that does not generate the reals?

6 votes
Accepted

Determining whether a graph is bipartite or not

5 votes

Elementary proof of compact space = exhaustible space?

5 votes

Different ways to cite references in Mathematics

5 votes

Category of sets and multi-valued functions

5 votes

Example of two open balls such that the one with the smaller radius contains the one with the larger radius.

5 votes

An easy to understand definition of $\omega_1$?

5 votes
Accepted

Open covers of a topological space $X$

5 votes

-5^2 again, why oh why?

5 votes

Is this a finite set for which it is impossible to list its elements?

5 votes
Accepted

Is it decidable whether a classically valid first-order formula is also intuitionistically valid?

4 votes

Definition of an interval in a poset

4 votes
Accepted

Does $\langle\mathbb{Q},<\rangle\cong\langle\mathbb{Q}\times\{{1,0}\},<_{lex}\rangle$?

4 votes
Accepted

Fake proof of $\mathbb{R}$ being countable

4 votes

Why do we care about non-$T_0$ spaces?

4 votes
Accepted

Difficulty of countable vs. uncountable sets proof?

4 votes
Accepted

Every nonstandard model of arithmetic has an element which is a multiple of every $n\in \Bbb N$.

4 votes
Accepted

Is there a constructive proof for Heine Borel Theorem?

3 votes

Guessing the value of $n$

3 votes
Accepted

$S, f(S), f(f(S)),...$

3 votes

Show that if taken 14 number from 1 to 25 at least one of them is multiple of another