Ivan Feshchenko's user avatar
Ivan Feshchenko's user avatar
Ivan Feshchenko's user avatar
Ivan Feshchenko
  • Member for 9 years, 11 months
  • Last seen more than 1 year ago
  • Kyiv, Ukraine
28 votes
2 answers
3k views

Can a countable union of two-element sets be uncountable?

19 votes
2 answers
2k views

Can we take a supremum over all Hilbert spaces?

8 votes
2 answers
877 views

Continuous linear functionals and the Axiom of Choice

5 votes
0 answers
267 views

Completeness of the space $L^p$ and the Axiom of Countable Choice

5 votes
1 answer
360 views

Inverse marginal property of a collection of $\sigma$-algebras

5 votes
2 answers
2k views

Extension of bounded linear operators

3 votes
0 answers
381 views

Dissection of a polygon into convex polygons

2 votes
0 answers
344 views

When is the sum of complemented subspaces complemented?

2 votes
0 answers
165 views

Algebraic connectivity of the path $P_n$

2 votes
1 answer
447 views

Can we choose an element from a class?

0 votes
1 answer
463 views

Is a function needed here?

0 votes
1 answer
308 views

Can we choose a sequence of Hilbert spaces?