Department of

# Mathematics

Seminar Calendar
for events the day of Monday, February 27, 2017.

.
events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
     January 2017          February 2017            March 2017
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  3  4
8  9 10 11 12 13 14    5  6  7  8  9 10 11    5  6  7  8  9 10 11
15 16 17 18 19 20 21   12 13 14 15 16 17 18   12 13 14 15 16 17 18
22 23 24 25 26 27 28   19 20 21 22 23 24 25   19 20 21 22 23 24 25
29 30 31               26 27 28               26 27 28 29 30 31



Monday, February 27, 2017

4:00 pm in 245 Altgeld Hall,Monday, February 27, 2017

#### Algebra, Combinatorics, Geometry

###### Hal Schenck (Department of Mathematics, University of Illinois)

Abstract: I'll give an overview of the spectacular success of algebraic methods in studying problems in discrete geometry and combinatorics. First we'll discuss the face vector (number of vertices, edges, etc.) of a convex polytope and recall Euler's famous formula for polytopes of dimension 3. Then we'll discuss graded rings, focusing on polynomial rings and quotients. Associated to a simplicial polytope P (every face is "like" a triangle) is a graded ring called the Stanley-Reisner ring, which "remembers" everything about P, and gives a beautiful algebra/combinatorics dictionary. I will sketch Stanley's solution to a famous conjecture using this machinery, and also touch on connections between P and toric varieties, which are objects arising in algebraic geometry.

4:00 pm in 243 Altgeld Hall,Monday, February 27, 2017

#### "The minimal number of periodic Reeb orbits as a cuplength

###### Jean Gutt (University of Georgia)

Abstract: I will present the recent result with P.Albers and D.Hein that every graphical hypersurface in a prequantization bundle over a symplectic manifold M pinched between two circle bundles whose ratio of radii is less than \sqrt{2} carries either one short simple periodic orbit or carries at least cuplength(M)+1 simple periodic Reeb orbits.

5:00 pm in 241 Altgeld Hall,Monday, February 27, 2017

#### Quasidiagonality of Nuclear C*-Algebras

###### Chris Linden (UIUC Math)

Abstract: We continue from last time with Schafhauser's proof.