# Tag Info

### Non-analytically measurable set in $\Delta^1_2$

You write: I can prove that such a set exists but just wondering if there's a (fairly) concrete example. The following might just be the proof you allude to, but I think it is fairly concrete: A set ...
• 21.3k
Accepted

### A continuous map relating co-constructible reals

By "formula" I will mean "formula of set theory with ordinal parameters." Note that "ordinal parameters" is equivalent to "constructible parameters" for our ...
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### Borel $\sigma$-algebras on paths of bounded variation
I think there is a problem with a mere semi-norm. The constant functions have variation distance $0$ from each other. Any variation-open set contains either all the constants, or none of them. ...