### Random walk on the simple symmetric exclusion process

Probability Seminar

22nd November 2019, 3:30 pm – 4:30 pm

Fry Building, LG.22

In a joint work with Marcelo R. Hilário and Augusto Teixeira, we investigate the long-term behavior of a random walker evolving on top of the simple symmetric exclusion process (SSEP) at equilibrium. At each jump, the random walker is subject to a drift that depends on whether it is sitting on top of a particle or a hole. The asymptotic behavior is expected to depend on the density $\rho$ in $[0, 1]$ of the underlying SSEP.

Our first result is a law of large numbers (LLN) for the random walker for all densities $\rho$ except for at most two values $\rho_-$ and $\rho_+$ in $[0, 1]$, where the speed (as a function fo the density) possibly jumps from, or to, 0. Second, we prove that, for any density corresponding to a non-zero speed regime, the fluctuations are diffusive and a Central Limit Theorem holds. For the special case in which the density is $1/2$ and the jump distribution on an empty site and on an occupied site are symmetric to each other, we prove a LLN with zero limiting speed.

Our main results extend to environments given by a family of independent simple symmetric random walks in equilibrium.

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