Department of

# Mathematics

Seminar Calendar
for events the day of Friday, February 27, 2015.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
     January 2015          February 2015            March 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    1  2  3  4  5  6  7    1  2  3  4  5  6  7
4  5  6  7  8  9 10    8  9 10 11 12 13 14    8  9 10 11 12 13 14
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Friday, February 27, 2015

4:00 pm in 147 Altgeld Hall,Friday, February 27, 2015

#### Weak order chains for strongly solvable spherical subgroups

###### Michael Joyce   [email] (Tulane University)

Abstract: An algebraic subgroup $H$ of a reductive algebraic group $G$ is spherical if there exists a Borel subgroup $B$ of $G$ such that $BH$ is dense in $G$. Spherical subgroups play an important role in algebraic geometry and representation theory since they are broad enough to include many interesting subgroups (parabolic subgroups, symmetric subgroups, maximal unipotent subgroups) yet restrictive enough to possess a combinatorial structure theory. A spherical subgroup $H$ is strongly solvable if it is contained in a Borel subgroup $G$. Building on work of Avdeev, who gave a new classification of strongly solvable spherical subgroups, and Gandini and Pezzini, who parameterized the $H$-orbits on the flag variety $G/B$, we describe the maximal chains in certain intervals of the weak order for $H$. The primary application is to give the cohomology class of the closure of an $H$-orbit in the Schubert basis of the flag variety.

4:00 pm in 241 Altgeld Hall,Friday, February 27, 2015

#### Tame Topology and O-minimal Structures

###### Travis Nell (UIUC Math)

Abstract: Lou van den Dries isolated the notion of O-minimality, a notion of tameness that includes the semialgebraic sets among many others. We will consider the basic properties of an O-minimal structure, cell decomposition, Euler characteristic, and O-minimal groups. There will also be examples due to Lou van den Dries, Macyntyre, and Wilkie.