2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/58081We consider the motion of a particle in a two-dimensional spatially homogeneous mixing potential and show that its momentum converges to the Brownian motion on a circle. This complements the limit theorem of Kesten and Papanicolaou \cite{KP} proved in dimensions $d\ge 3$.Mathematical PhysicsProbabilitytext