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Timeline for Commuting supremum and expectation

Current License: CC BY-SA 2.5

16 events
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Jan 13, 2023 at 17:45 comment added ABIM @Did Was an answer on this ever settled?
Apr 13, 2017 at 12:58 history edited CommunityBot
replaced http://mathoverflow.net/ with https://mathoverflow.net/
Jun 19, 2011 at 10:42 comment added Did @zhoraster: Not interested in answering the question in my comment? Let me recall it: in the first line of your answer, why should $M$ be measurable?
Jun 19, 2011 at 10:40 comment added Did @Johannes: Not interested in answering the question in my comment? Let me recall it: why should $M$ be measurable?
Feb 15, 2011 at 13:27 comment added Did .../... Assume for instance that $\Omega\subseteq U$ and fix $V\subset\Omega$. Define the family $(X_a)$ by $X_a(\omega)=1$ if $a\in V$ and $\omega=a$, and $X_a(\omega)=0$ otherwise. Then $M(\omega)=1$ if $\omega\in V$ and $M(\omega)=0$ otherwise, hence $M=\mathbf{1}_V$ and, since $V$ can be any subset of $\Omega$, it may well happen that $M:(\Omega,\mathcal{F})\to(\mathbb{R},\mathcal{B}(\mathbb{R}))$ is not measurable. If you could explain what I miss, I would be grateful.
Feb 15, 2011 at 13:27 comment added Did @Johannes @zhoraster Sorry to be late at the party but I am afraid I do not understand what is going on. Let me stick to the (apparently) definitive version of Johannes' post, above this comment. One starts with $U\subseteq \mathbb{R}$ and with a family $(X_a)$ of real valued random variables $X_a:(\Omega,\mathcal{F})\to(\mathbb{R},\mathcal{B}(\mathbb{R}))$, indexed by $a\in U$, and one introduces $M=\sup_{a\in U}X_a$. I wonder why $M$ should be measurable in the first place, clearly or not. :-) .../...
Dec 8, 2010 at 10:38 comment added zhoraster Looks good, I don't see a mistake.
Dec 8, 2010 at 8:19 vote accept Johannes
Dec 5, 2010 at 13:07 vote accept Johannes
Dec 5, 2010 at 13:07
Dec 4, 2010 at 16:50 history edited Johannes CC BY-SA 2.5
added 134 characters in body
Dec 4, 2010 at 16:37 history edited Johannes CC BY-SA 2.5
clearify the question and summerize the given answers; added 10 characters in body; added 2 characters in body
Dec 4, 2010 at 16:28 history edited Johannes CC BY-SA 2.5
deleted 3 characters in body; edited title; Post Made Community Wiki
Dec 3, 2010 at 19:19 answer added zhoraster timeline score: 4
Dec 2, 2010 at 13:52 answer added FraoncoisL timeline score: -1
Dec 2, 2010 at 9:37 history edited Johannes CC BY-SA 2.5
deleted 114 characters in body
Dec 2, 2010 at 8:45 history asked Johannes CC BY-SA 2.5