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Logic Seminar

Monday, January 11, 2021
12:00pm to 1:00pm
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Online Event
A new regularity property of the Haar null ideal
Zoltán Vidnyánszky, Department of Mathematics, Caltech,

Christensen's Haar null ideal is a well-behaved generalization of Haar null sets to groups, which admit no Haar measure. We show that in the group ZωZω, every Haar positive (that is, non-Haar null) analytic set contains a Haar positive closed set. Using this result, we determine the exact Wadge class of the family of Haar null closed subsets of ZωZω.

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