Department of

# Mathematics

Seminar Calendar
for events the day of Friday, April 17, 2015.

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events for the
events containing

More information on this calendar program is available.
Questions regarding events or the calendar should be directed to Tori Corkery.
      March 2015             April 2015              May 2015
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6  7             1  2  3  4                   1  2
8  9 10 11 12 13 14    5  6  7  8  9 10 11    3  4  5  6  7  8  9
15 16 17 18 19 20 21   12 13 14 15 16 17 18   10 11 12 13 14 15 16
22 23 24 25 26 27 28   19 20 21 22 23 24 25   17 18 19 20 21 22 23
29 30 31               26 27 28 29 30         24 25 26 27 28 29 30
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Friday, April 17, 2015

4:00 pm in 147 Altgeld Hall,Friday, April 17, 2015

#### Staircase diagrams and enumeration of smooth Schubert varieties

###### Edward Richmond   [email] (Oklahoma State Math)

Abstract: Staircase diagrams are certain partially ordered sets defined over a graph. When the graph is the Dynkin diagram of a simple Lie group, these diagrams correspond to smooth Schubert varieties of the corresponding flag variety. Staircase diagrams have two applications. First, they encode much of the geometric and combinatorial data of Schubert varieties. Second, these diagrams give a way to calculate the generating series for the number of smooth Schubert varieties of any type. This extends the work of M. Haiman who calculated this generating series in type A. This talk is on joint work with W. Slofstra.

4:00 pm in 241 Altgeld Hall,Friday, April 17, 2015

#### Thompson's Groups and Knot Diagrams

###### Malik Obeidin (UIUC Math)

Abstract: In 1965, Richard J. Thompson introduced three finitely presented groups, $F \subset T \subset V$, which have a number of curious group-theoretic properties. These groups have been rediscovered by topologists on several occasions - most recently, Vaughan Jones showed that the group $F$ encodes knot diagrams in a particular way. I will discuss the group $F$, its descriptions, and its possible applications to studying knots.