Department of

# Mathematics

Seminar Calendar
for events the day of Friday, November 18, 2005.

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Questions regarding events or the calendar should be directed to Tori Corkery.
     October 2005          November 2005          December 2005
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1          1  2  3  4  5                1  2  3
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Friday, November 18, 2005

4:00 pm in 341 Altgeld Hall,Friday, November 18, 2005

#### The Polishable Subgroups Problem and Hjorth's Conjecture

###### Su Gao (University of North Texas, Denton)

Abstract: Farah and Solecki asked if every uncountable Polish group contains Polishable subgroups of arbitrarily high Borel rank. Hjorth gave a positive answer for abelian groups and went on to make the following conjecture: There is an uncountable Polish group all of whose abelian subgroups are discrete. I will state a theorem that proves Hjorth's conjecture and sketch its proof. On the other hand, we show that the Farah-Solecki question could be approached otherwise.