Two Problems in Mathematical Physics: Villani's Conjecture and a Trace Inequality for the Fractional Laplacian

Dissertation Defense
Monday, August 29, 2011 - 11:00am for 1 hour (actually 50 minutes)
Skiles 006
Amit Einav – School of Mathematics, Georgia Tech
Amit Einav
The presented work deals with two distinct problems in the field of Mathematical Physics, and as such will have two parts addressing each problem. The first part is dedicated to an 'almost' solution of Villani's conjecture, a known conjecture related to a Statistical Mechanics model invented by Kac in 1956, giving a rigorous explanation of some simple cases of the Boltzman equation. In 2003 Villani conjectured that the time it will take the system of particles in Kac's model to equalibriate is proportional to the number of particles in the system. Our main result in this part is an 'almost proof' of that conjecture, showing that for all practical purposes we can consider it to be true. The second part of the presentation is dedicated to a newly developed trace inequality for the fractional Laplacian, connecting between the fractional Laplacian of a function and its restriction to the intersection of the hyperplanes x_n =...= x_n-j+1 = 0 , where 1 <= j < n. The newly found inequality is sharp and the functions that attain inequality in it are completely classified.