Bernard Derrida - Ecole Normale Supérieure de Paris
Wednesday, October 6, 10:45AM (Zoom meeting starts at 10:30)
“Renormalization and disorder : a simple toy model”
After a short review of our understanding of how a weak disorder or a low density of impurities affect the universality class of a phase transition, I will discuss a simple tree-like toy model for which one can prove that, due to disorder, the depinning transition becomes an infinite order transition of the Berezinski-Kosterlitz-Thouless type. This toy model was introduced to understand the depinning transition of a line from a random substrate, one of the simplest problems in the theory of disordered systems. This depinning transition has a long history among physicists and mathematicians. Still the nature of the transition, one of the central questions of the problem, remains unsolved. Chen, Dagard, Derrida, Hu, Lifshits, Shi, The Annals of Probability, 2021 Chen, Dagard, Derrida, Shi Journal of Physics A: Mathematical and Theoretical, 2020