User Iian Smythe

16 votes

4 answers

4k views

How much does the absolute value of an operator behave like an absolute value?

asked Jul 8, 2014 at 17:52

14 votes

2 answers

690 views

Why do the projections in the Calkin algebra not form a lattice?

asked Jun 17, 2014 at 20:16

11 votes

1 answer

599 views

Approximating a real in the ground model

asked Dec 5, 2020 at 16:13

11 votes

1 answer

335 views

Uncountable homogeneous rectangles for subsets of $\omega_2\times\omega_2$

asked Jul 6, 2021 at 2:12

9 votes

1 answer

317 views

Decidability of the Hilbert lattice and quantum logic

asked Mar 17, 2015 at 15:19

9 votes

1 answer

325 views

Countable $\mathbf\Sigma^1_2$ equivalence relations

asked Mar 16, 2018 at 19:51

8 votes

1 answer

568 views

Is $\ell^\infty$ Polishable?

asked Jun 11, 2014 at 21:42

8 votes

1 answer

402 views

Nonexistence of generic objects over $L(\mathbb{R})$

asked Apr 24, 2016 at 19:32

8 votes

2 answers

623 views

Extracting subsequences in Banach spaces, along an ultrafilter?

asked Jul 6, 2016 at 17:54

8 votes

1 answer

391 views

Complexity of the set of closed subsets of an analytic set

asked Apr 19, 2019 at 18:08

7 votes

2 answers

682 views

Set of perfect subsets of a Borel set

asked Jul 31, 2019 at 0:44

7 votes

1 answer

173 views

Existence of Borel uniformization for coanalytic set with non-$K_\sigma$ sections

asked Dec 22, 2023 at 18:44

7 votes

0 answers

189 views

Examples of analytic $\mathcal{I}$-mad families

asked May 18, 2016 at 15:34

6 votes

1 answer

400 views

Products and Gale-Stewart games

asked Nov 9, 2017 at 4:18

6 votes

1 answer

312 views

Cohen generics over the ground model still Cohen over other generic extensions?

asked Jul 19, 2018 at 16:18

6 votes

2 answers

475 views

Complete atomless Boolean algebras with abelian automorphism group

asked Aug 25, 2018 at 19:38

6 votes

2 answers

1k views

Characterization of ideals in the bounded operators

asked Jun 20, 2014 at 3:51

6 votes

3 answers

454 views

Can every $\mathcal{L}_{\omega_1,\omega}$ formula be expressed as a type? What about canonical forms?

asked Jun 19, 2012 at 21:24

6 votes

1 answer

276 views

Is the ideal of compact operators strongly Borel?

asked Jun 20, 2013 at 1:47

6 votes

0 answers

337 views

A characterization of Mathias reals

asked Jun 5, 2014 at 0:49

6 votes

0 answers

80 views

Countable companions for Polish locally compact groups and their orbit equivalence relations

asked Mar 9, 2023 at 22:16

6 votes

1 answer

270 views

Which Lie groups are covers of matrix groups?

asked May 8 at 2:52

5 votes

1 answer

184 views

Is there a standard Borel space of finitely branching real trees?

asked Nov 9, 2022 at 18:10

5 votes

0 answers

185 views

The (global) theory of Borel equivalence relations

asked Jul 23, 2014 at 16:56

5 votes

1 answer

442 views

Buying more absoluteness for countable transitive models?

asked Sep 9, 2018 at 20:04

5 votes

2 answers

271 views

Von Neumann's theorem on realizing automorphisms of the measure algebra

asked Jul 6, 2018 at 2:17

5 votes

1 answer

211 views

Equivalence of questions regarding restrictions of pure states

asked Jun 28, 2016 at 20:02

5 votes

1 answer

273 views

Is the set of subsequences of branches through a tree Borel?

asked Mar 8, 2016 at 2:33

4 votes

3 answers

276 views

Closed free subgroups of the automorphism group of the countable atomless boolean algebra

asked May 29, 2018 at 17:57

4 votes

0 answers

240 views

Interesting examples of countable support iteration of ccc forcings

asked Dec 27, 2017 at 18:30

Stack Exchange Network

54 Questions

How much does the absolute value of an operator behave like an absolute value?

Why do the projections in the Calkin algebra not form a lattice?

Approximating a real in the ground model

Uncountable homogeneous rectangles for subsets of $\omega_2\times\omega_2$

Decidability of the Hilbert lattice and quantum logic

Countable $\mathbf\Sigma^1_2$ equivalence relations

Is $\ell^\infty$ Polishable?

Nonexistence of generic objects over $L(\mathbb{R})$

Extracting subsequences in Banach spaces, along an ultrafilter?

Complexity of the set of closed subsets of an analytic set

Set of perfect subsets of a Borel set

Existence of Borel uniformization for coanalytic set with non-$K_\sigma$ sections

Examples of analytic $\mathcal{I}$-mad families

Products and Gale-Stewart games

Cohen generics over the ground model still Cohen over other generic extensions?

Complete atomless Boolean algebras with abelian automorphism group

Characterization of ideals in the bounded operators

Can every $\mathcal{L}_{\omega_1,\omega}$ formula be expressed as a type? What about canonical forms?

Is the ideal of compact operators strongly Borel?

A characterization of Mathias reals

Countable companions for Polish locally compact groups and their orbit equivalence relations

Which Lie groups are covers of matrix groups?

Is there a standard Borel space of finitely branching real trees?

The (global) theory of Borel equivalence relations

Buying more absoluteness for countable transitive models?

Von Neumann's theorem on realizing automorphisms of the measure algebra

Equivalence of questions regarding restrictions of pure states

Is the set of subsequences of branches through a tree Borel?

Closed free subgroups of the automorphism group of the countable atomless boolean algebra

Interesting examples of countable support iteration of ccc forcings