In this talk we will discuss some open questions and some recent results of sharp isoperimetric type.  The rigidity and stability statements and their consequences are perhaps more interesting than the inequalities.  One particular rigidity result is that the only compact Riemannian surfaces with boundary where almost every pair of geodesics intersect exactly once are the round hemispheres.

Inhomogeneous dependency modelling with time varying copulae

In his last letter to Hardy, Ramanujan defined 17 peculiar functions which are now referred to as his mock theta functions. Although these mysterious functions have been investigated by many mathematicians over the years, many of their most basic properties remain unknown. This inspired Freeman Dyson to proclaim:

"The mock theta-functions give us tantalizing hints of a grand synthesis still to be discovered. Somehow it should be possible to build them into a coherent group-theoretical structure, analogous to the structure of modular forms which Hecke built around the old theta-functions of Jacobi. This remains a challenge for the future."
- Freeman Dyson 1987, Ramanujan Centenary Conference

Here we announce a solution to Dyson's "challenge for the future" by providing the "coherent group-theoretical structure" that Dyson desired in his plenary address at the 1987 Ramanujan Centenary Conference.

In joint work with Ken Ono, we show that Ramanujan's mock theta functions, as well a natural generalized infinite class of mock theta functions may be completed to obtain Maass forms, a special class of modular forms. We then use these results to prove theorems about Dyson's partition ranks. In particular, we shall prove the 1966 Andrews-Dragonette Conjecture, whose history dates to Ramanujan's last letter to Hardy, and we shall also prove that Dyson's ranks `explain' Ramanujan's partition congruences in an unexpected way.

Detroit MI, April 2001.
A woman is found stabbed to death in the kitchen of her apartment. The police find that a video recorder in the family room was recording during the murder, but the camera lens cap was on and, as a result, the video portion of the recording reveals nothing. The audio channel of the recording, however, has captured the entire crime. Unfortunately, a stereo was playing loud schmaltzy music during the conversation leading up to the assault, and the speech on the recording cannot be understood. Fortunately, the police have the tape that was playing at the time, but traditional approaches for removing the interfering music from the mixture fail.
Princeton NJ, June 2002.

Murder victim gets the last word - case closed.

In this talk I will discuss the sparse revolution which is occurring in signal processing which is allowing researchers to solve systems of equations with more unknowns than constraints. We've all been taught that if we have 2 unknowns, we require 2 equations to solve for the unknowns. For 3 unknowns, we need 3 equations (and 4 require 4, and so on...). This is not true - as long as you're willing to cheat. For example, we 'cheat' in cocktail parties when we listen to one person while a dozen speak in the background. Mathematically, we would need 13 ears to eliminate the dozen unwanted speakers to allow us to focus on the one speaker of interest. The DUET Blind Source Separation Algorithm mimics this human auditory ability in that it can separate an arbitrary number of sources from just two mixtures (such as those heard by two ears in a cocktail party). I will reveal how we use sparsity to cheat and thus solve the problem of more unknowns than equations. Also, I will discuss various related modifications of DUET, one of which was used to solve the above murder case. This talk will feature a live demonstration of DUET.