“…In that case, a functional limit theorem requires the convergence in non-standard Skorokhod topologies such as the M 1 -Skorokhod topology. Non-linear (β = 1) stochastic systems of the type (1.6) driven by Brownian motion, Z = B, have been studied in recent years both in physical and mathematical literature, see Lindner (2007Lindner ( , 2008Lindner ( , 2010; Lisý et al (2014) for the analysis for β = 1, 2, 3, 5, Baule and Sollich (2012); Touchette et al (2010); de Gennes (2005); Hayakawa (2005); Kawarada and Hayakawa (2004); Mauger (2006) for the important case of dry (Coulomb) friction β = 0, and Goohpattader and Chaudhury (2010) for experiments and simulations for the dry friction β = 0 and irregular friction β = 0.4. The main goal of these papers was to determine on the physical level of rigour how the so-called effective diffusion coefficient, which is roughly speaking the variance of the particle's position, depends on ε.…”