A universal exponent for Brownian entropic repulsion

Abstract

We investigate the extent to which the phenomenon of Brownian entropic repulsion is universal. Consider a Brownian motion conditioned on the event $\mathcal{E}$ -- that its local time is bounded everywhere by 1. This event has probability zero and so must be approximated by events of positive probability. We prove that several natural quantities, in particular the speed of the process, are highly sensitive to the approximation procedure, and hence are not universal. However, we also propose an exponent $\kappa$ -- which measures the strength of the entropic repulsion by evaluating the probability that a particular point comes close to violating the condition $\mathcal{E}$. We show that $\kappa=3$ for several natural approximations of $\mathcal{E}$, and conjecture that $\kappa=3$ is universal in a sense that we make precise.