Previous Conferences & Workshops

Apr
14
2011

Galois Representations and Automorphic Forms Seminar

The Bernstein Center of the Category of Smooth W(k)[GL_n(F)]-Modules
David Helm
2:15pm|S-101

The Bernstein center plays a role in the representation theory of locally profinite groups analogous to that played by the center of the group ring in the representation theory of finite groups. When F is a finite extension of Q_p, we discuss the...

Apr
13
2011

Members’ Seminar

Intersections of Polynomial Orbits, and a Dynamical Mordell-Lang Conjecture
Michael Zieve
2:00pm|S-101

Let f and g be nonlinear polynomials (in one variable) over the complex numbers. I will show that, if there exist complex numbers a and b for which the orbits {a, f(a), f(f(a)), ...} and {b, g(b), g(g(b)), ...} have infinite intersection, then f and...

Apr
11
2011

Computer Science/Discrete Mathematics Seminar I

Graph Sparsification by Edge-Connectivity and Random Spanning Trees
Nick Harvey
11:15am|S-101

A "sparsifier" of a graph is a weighted subgraph for which every cut has approximately the same value as the original graph, up to a factor of (1 +/- eps). Sparsifiers were first studied by Benczur and Karger (1996). They have wide-ranging...

Apr
08
2011

Geometry/Dynamical Systems Seminar

The Dehn Function of SL(n;Z)
4:00pm|S-101

The Dehn function is a group invariant which connects geometric and combinatorial group theory; it measures both the difficulty of the word problem and the area necessary to fill a closed curve in an associated space with a disc. The behavior of the...

Apr
06
2011

Mathematical Conversations

"We know that God exists because mathematics is consistent and we know that the devil exists because we cannot prove the consistency." -- Andre Weil
6:00pm|S-101
Apr
06
2011

Workshop on Topology: Identifying Order in Complex Systems

Persistent Cohomology and Circular Coordinates
Vin de Silva
4:30pm|University of Pennsylvania, David Rittenhouse Lab., Room A6

High-dimensional data sets often carry meaningful low-dimensional structures. There are different ways of extracting such structural information. The classic (circa 2000, with some anticipation in the 1990s) strategy of nonlinear dimensionality...