Saint Petersburg Univ and Tel Aviv University
Date(s) : 06/03/2017 iCal
10 h 00 min - 11 h 00 min
Let u be a harmonic function on the plane. The Liouville theorem claims that if |u| is bounded on the whole plane, then u is identically constant. At the same moment for any angle on the plane R^2, there exist a harmonic function that is non-constant and is bounded outside the angle. It appears that if u is a harmonic function on a lattice Z^2, and |u| < 1 on 99,99% of Z^2, then u is a constant function. In particular there are no (non-constant) discrete harmonic functions bounded outside a sufficiently small angle. Based on a joint work (in progress) with L. Buhovsky, Eu. Malinnikova and M. Sodin.