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UID:20260825T024902EDT-1804EdB2xD@132.216.98.100
DTSTAMP:20260825T064902Z
DESCRIPTION:Title: Ideals with and without definable selectors\n	 \n\nAbstra
 ct:\n\nLet X be a Polish space\, and consider an ideal I on X. We can form
  the quotient of the Borel subsets of X by the equivalence relation which 
 identifies sets which agree up to a set in I. For which ideals is it possi
 ble to select\, in some definable manner\, a representative for each equiv
 alence class? One example where this is possible is the ideal of Lebesgue 
 null sets: This follows from Lebesgue's Density Theorem. Another example i
 s the meager ideal. In this talk I will present an abstract property of id
 eals which ensures that a selector can be defined\; on the other hand\, no
  definable selector exists for the ideal of countable sets. I will further
  present some consistency results.\n	(Joint work with Sandra Müller\, Phili
 pp Schlicht\, and Thilo Weinert.)\n
DTSTART:20190205T193000Z
DTEND:20190205T203000Z
LOCATION:Room 920\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:David Schrittesser (Vienna) 
URL:https://www.mcgill.ca/mathstat/channels/event/david-schrittesser-vienna
 -293956
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