Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with descriptive-set-theory
Search options not deleted
user 5903
Descriptive Set Theory is the study of definable subsets of Polish spaces, where definable is taken to mean from the Borel or projective hierarchies. Other topics include infinite games and determinacy, definable equivalence relations and Borel reductions between them, Polish groups, and effective descriptive set theory.
6
votes
Accepted
Continuously selecting elements from unordered pairs
In this paper Van Mill and Wattel proved that the existence of a continuous selection characterizes orderability in the class of compact Hausdorff spaces.
- 11.4k
3
votes
Accepted
CH and the density topology on $\mathbb{R}$
According to your first reference your space is dense with respect to the density topology; this implies that, in $Y$, the closure of $Y\cap(0,\infty)$ is $Y\cap[0,\infty)$; the latter set is not open …
- 11.4k
3
votes
Accepted
Subsets of the Cantor set
To answer the question: every point of $U$ is an accumulation point of $D\cap U$, hence there are continuum many accumulation points. The ambient space $X$ plays no role here; everything takes place i …
- 11.4k
8
votes
Accepted
Can totally inhomogeneous sets of reals coexist with determinacy?
In Rigid Borel sets and better quasiorder theory (Logic and combinatorics, Proc. AMS-IMS-SIAM Conf., Arcata/Calif. 1985, Contemp. Math. 65, 199-222 (1987), zbMath review here) Fons van Engelen, Arnold …
- 11.4k
5
votes
Accepted
Is there a metric separable space with the following properties...?
Let $X$ be a Bernstein subset of $\mathbb{R}$, so $X$ and its complement intersect every uncountable closed set in $\mathbb{R}$.
Let $f:X\to\mathbb{R}$ be continuous and assume $f[X]$ is uncountable. …
- 11.4k
9
votes
Accepted
Is it true that $\mathit{MA}(\omega_1)$ iff $\omega_1<\mathfrak{p}$?
Q1: No, see Between Martin's Axiom and Souslin's Hypothesis by Kunen and Tall. Note: Bell proved in The combinatorial principle $P(\mathfrak{c})$ that $\mathfrak{p}>\aleph_1$ is equivalent to $\mathsf …
- 11.4k