Department of

# Mathematics

Seminar Calendar
for events the day of Monday, September 30, 2013.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
     August 2013           September 2013          October 2013
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3    1  2  3  4  5  6  7          1  2  3  4  5
4  5  6  7  8  9 10    8  9 10 11 12 13 14    6  7  8  9 10 11 12
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Monday, September 30, 2013

10:00 am in 145 Altgeld Hall,Monday, September 30, 2013

#### Positive loops and orderability in contact geometry

###### Peter Weigel (Purdue University Math)

Abstract: Orderability of contact manifolds is related in some non-obvious ways to the topology of a contact manifold V. We know, for instance, that if V admits a 2-subcritical Stein filling, it must be non-orderable. By way of contrast, in this talk I will discuss ways of modifying Liouville structures for high-dimensional V so that the result is always orderable. The main technical tool is a Morse-Bott Floer theoretic growth rate, which has some parallels with Givental's nonlinear Maslov index. I will also discuss a generalization to the relative case, and applications to bi-invariant metrics on Cont(V).

4:00 pm in 241 Altgeld Hall,Monday, September 30, 2013

#### Finite generating partitions for countable group actions

###### Anush Tserunyan (Illinois)

Abstract: Consider a continuous action of a countable group G on a Polish space space X. A countable Borel partition P of X is called a generator if GP={gA: g in G, A in P} generates the Borel sigma-algebra of X. For G=Z, the Kolmogorov-Sinai theorem gives a measure-theoretic obstruction to the existence of finite generators: they don't exist in the presence of an invariant probability measure with infinite entropy. It was asked by Weiss in the late 80s whether the nonexistence of any invariant probability measure would guarantee the existence of a finite generator. We show that the answer is positive for an arbitrary countable group G and sigma-compact X (in particular, for locally compact X).

5:00 pm in 241 Altgeld,Monday, September 30, 2013

#### Compact actions and uniqueness of the group measure space decomposition of II$_1$ factors (after Adrian Ioana)

###### Bogdan Udrea (UIUC Math)

5:00 pm in 241 Altgeld,Monday, September 30, 2013

Abstract: TBA