Universality and non-universality of mobility in heterogeneous single-file systems and Rouse chains

We study analytically the tracer particle mobility in single-file systems with distributed friction constants. Our system serves as a prototype for non-equilibrium, heterogeneous, strongly interacting Brownian systems. The long time dynamics for such a single-file setup belongs to the same universality class as the Rouse model with dissimilar beads. The friction constants are drawn from a density $\varrho(\xi)$ and we derive an asymptotically exact solution for the mobility distribution $P[\mu_0(s)]$, where $\mu_0(s)$ is the Laplace-space mobility. If $\varrho$ is light-tailed (first moment exists) we find a self-averaging behaviour: $P[\mu_0(s)]=\delta[\mu_0(s)-\mu(s)]$ with $\mu(s)\propto s^{1/2}$. When $\varrho(\xi)$ is heavy-tailed, $\varrho(\xi)\simeq \xi^{-1-\alpha} \ (0<\alpha<1)$ for large $\xi$ we obtain moments $\langle [\mu_s(0)]^n\rangle \propto s^{\beta n}$ where $\beta=1/(1+\alpha)$ and no self-averaging. The results are corroborated by simulations.