Timeline for Topological proof that a Vitali set is not Borel
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 25, 2020 at 21:14 | comment | added | Piotr Hajlasz | This might be a slightly overly detailed answer, Not at all. I would expect all answers to be detailed as this. Most of the answers on MathOverflow lack details making them basically useless. Thank you. I just added OP's question to the homework in my measure theory course and I included hints that follow your answer. | |
| May 25, 2020 at 11:03 | comment | added | YCor | (yes, and sorry for the typo you corrected: I should have quoted "$V$ is co-meager in some open interval) | |
| May 25, 2020 at 11:01 | comment | added | Wojowu | @YCor Thank you for these remarks! Yes, this is precisely what I meant with "comeager in an open interval". | |
| May 25, 2020 at 10:53 | comment | added | YCor | Also I guess that "$V$ is meager in some open interval" should be understood as "there exists a nonempty open interval $I$ such that $V\cap I$ is comeager in $I$". (It took me a while to unravel so I'm adding this as a comment.) | |
| May 25, 2020 at 10:48 | comment | added | YCor | Just for completeness: a subset $Y$ of a topological space $X$ has the Baire property, or is almost open in $X$ if it differs from an open subset by a meager subset, i.e., can be written as $U\triangle M$ with $U$ open and $M$ meager. And meager means, contained in a countable union of closed subsets with empty interior. | |
| May 25, 2020 at 10:02 | vote | accept | abx | ||
| May 25, 2020 at 9:55 | history | answered | Wojowu | CC BY-SA 4.0 |