Hydrodynamic limit of zero range processes among random conductances on the supercritical percolation cluster

We consider i.i.d. random variables {\omega (b):b \in E_d} parameterized by the family of bonds in Z^d, d>1. The random variable \omega(b) is thought of as the conductance of bond b and it ranges in a finite interval [0,c_0]. Assuming the probability m of the event {\omega(b)>0} to be supercritical and denoting by C(\omega) the unique infinite cluster associated to the bonds with positive conductance, we study the zero range process on C(\omega) with \omega(b)-proportional probability rate of jumps along bond b. For almost all realizations of the environment we prove that the hydrodynamic behavior of the zero range process is governed by the nonlinear heat equation $\partial_t \rho= m \nabla \cdot (D \nabla\phi(\rho/m))$, where the matrix D and the function \phi are \omega--independent. We do not require any ellipticity condition.Comment: 30 pages, new results (see Appendix A), final versio

Random walks and exclusion processes among random conductances on random infinite clusters: homogenization and hydrodynamic limit

We consider a stationary and ergodic random field {\omega(b)} parameterized by the family of bonds b in Z^d, d>1. The random variable \omega(b) is thought of as the conductance of bond b and it ranges in a finite interval [0,c_0]. Assuming that the set of bonds with positive conductance has a unique infinite cluster C, we prove homogenization results for the random walk among random conductances on C. As a byproduct, applying the general criterion of \cite{F} leading to the hydrodynamic limit of exclusion processes with bond-dependent transition rates, for almost all realizations of the environment we prove the hydrodynamic limit of simple exclusion processes among random conductances on C. The hydrodynamic equation is given by a heat equation whose diffusion matrix does not depend on the environment. We do not require any ellipticity condition. As special case, C can be the infinite cluster of supercritical Bernoulli bond percolation.Comment: 24 pages. extensions and corrections. new titl

Spectral analysis of 1D nearest-neighbor random walks and applications to subdiffusive trap and barrier models

We consider a family X^{(n)}, n \in \bbN_+, of continuous-time nearest-neighbor random walks on the one dimensional lattice Z. We reduce the spectral analysis of the Markov generator of X^{(n)} with Dirichlet conditions outside (0,n) to the analogous problem for a suitable generalized second order differential operator -D_{m_n} D_x, with Dirichlet conditions outside a given interval. If the measures dm_n weakly converge to some measure dm_*, we prove a limit theorem for the eigenvalues and eigenfunctions of -D_{m_n}D_x to the corresponding spectral quantities of -D_{m_*} D_x. As second result, we prove the Dirichlet-Neumann bracketing for the operators -D_m D_x and, as a consequence, we establish lower and upper bounds for the asymptotic annealed eigenvalue counting functions in the case that m is a self--similar stochastic process. Finally, we apply the above results to investigate the spectral structure of some classes of subdiffusive random trap and barrier models coming from one-dimensional physics.Comment: Published on EJP. the Dirichlet-Neumann bracketing has been corrected. shorter, improved version. 35 page

Mott law as upper bound for a random walk in a random environment

We consider a random walk on the support of an ergodic simple point process on R^d, d>1, furnished with independent energy marks. The jump rates of the random walk decay exponentially in the jump length and depend on the energy marks via a Boltzmann-type factor. This is an effective model for the phonon-induced hopping of electrons in disordered solids in the regime of strong Anderson localization. Under mild assumptions on the point process we prove an upper bound of the asymptotic diffusion matrix of the random walk in agreement with Mott law. A lower bound in agreement with Mott law was proved in \cite{FSS}.Comment: 22 pages. Additional results and corrections

Hydrodynamic limit of a disordered lattice gas

We consider a model of lattice gas dynamics in the d-dimensional cubic lattice in the presence of disorder. If the particle interaction is only mutual exclusion and if the disorder field is given by i.i.d. bounded random variables, we prove the almost sure existence of the hydrodynamical limit in dimension d>2. The limit equation is a non linear diffusion equation with diffusion matrix characterized by a variational principle