Tel Aviv University, Colloquium Hello everyone, The next colloquium talk will be held on: Monday, 17/12/2012, 12:15, Schreiber 006, Tel Aviv University. Speaker: Lionel Levine (Cornell University) Title: Scaling Limit of the Abelian Sandpile The abstract is given below. Tea and coffee at 12:00, same room. Hope to see you there. For information about future colloquia, see <http://www.math.tau.ac.il/~ostrover/colloquium/colloq2012.html> Yours, Yaron ************************************* Abstract: Let n particles starting at the origin in Z^2 spread out by a deterministic rule: At each time step, each site with 4 or more particles sends one particle to each of its neighbors (North, South, East and West). The resulting final configuration has a complex fractal structure that remains mysterious. In a breakthrough work in 2011, Pegden and Smart proved existence of its scaling limit as n goes to infinity. Their insight was to ask which functions on R^2 can be expressed as limits of superharmonic functions from (1/n) Z^2 to (1/n^2) Z. I will discuss joint work with Pegden and Smart on the case of quadratic functions, where this question has a surprising and beautiful answer: the maximal such quadratics are classified by the circles in a certain Appolonian circle packing of R^2. --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: <ostrover@post.tau.ac.il>