The solution to the one dimensional Fisher-KPP equation (1937) u_t=Delta u+u(1-u) starting from a step initial condition, converges after centering by 2t - 3/2 log t to a traveling wave. The logarithmic correction term, and in particular the coefficient 3/2, was computed by Bramson (1978), through a connection with the maximum of branching Brownian motion. Recently, this computation proved crucial in the solution of a variety of problems: the law of the maximum of the critical Gaussian free field, the cover time of the 2-sphere by Brownian sausage, the maxima of the characteristic polynomials of random unitary matrices, and even the values of the Riemann zeta function on the critical line. These problems all share a hidden logarithmic (i.e., multiscale) correlation. In the talk I will describe these development and will emphasize the common philosophy in studying these very different models.
Penn Mathematics Colloquium
Wednesday, October 4, 2017 - 3:30pm
Ofer Zeitouni
Weizmann Institute and NYU