One-dimensional random field Kac's model: weak large deviations principle

We prove a quenched weak large deviations principle for the Gibbs measures of a Random Field Kac Model (RFKM) in one dimension. The external random magnetic field is given by symmetrically distributed Bernoulli random variables. The results are valid for values of the temperature, $\beta^{-1}$, and magnitude, $\theta$, of the field in the region where the free energy of the corresponding random Curie Weiss model has only two absolute minima $m_\beta$ and $Tm_\beta$. We give an explicit representation of the rate functional which is a positive random functional determined by two distinct contributions. One is related to the free energy cost ${\cal F}^*$ to undergo a phase change (the surface tension). The ${\cal F}^*$ is the cost of one single phase change and depends on the temperature and magnitude of the field. The other is a bulk contribution due to the presence of the random magnetic field. We characterize the minimizers of this random functional. We show that they are step functions taking values $m_\beta$ and $Tm_\beta$. The points of discontinuity are described by a stationary renewal process related to the $h-$extrema for a bilateral Brownian motion studied by Neveu and Pitman, where $h$ in our context is a suitable constant depending on the temperature and on magnitude of the random field. As an outcome we have a complete characterization of the typical profiles of RFKM (the ground states) which was initiated in [14] and extended in [16]

Spectral properties of integral operators in bounded, large intervals

We study the spectrum of one dimensional integral operators in bounded real intervals of length $2L$, for value of $L$ large. The integral operators are obtained by linearizing a non local evolution equation for a non conserved order parameter describing the phases of a fluid. We prove a Perron-Frobenius theorem showing that there is an isolated, simple minimal eigenvalue strictly positive for $L$ finite, going to zero exponentially fast in $L$. We lower bound, uniformly on $L$, the spectral gap by applying a generalization of the Cheeger's inequality. These results are usefulfor deriving spectral properties for non local Cahn-Hilliard type of equations in problems of interface dynamics.Comment: An serious error has been corrected and an author has been adde

Boundary driven Kawasaki process with long range interaction: dynamical large deviations and steady states

A particle system with a single locally-conserved field (density) in a bounded interval with different densities maintained at the two endpoints of the interval is under study here. The particles interact in the bulk through a long range potential parametrized by $\beta\ge 0$ and evolve according to an exclusion rule. It is shown that the empirical particle density under the diffusive scaling solves a quasi-linear integro-differential evolution equation with Dirichlet boundary conditions. The associated dynamical large deviation principle is proved. Furthermore, for $\beta$ small enough, it is also demonstrated that the empirical particle density obeys a law of large numbers with respect to the stationary measures (hydrostatic). The macroscopic particle density solves a non local, stationary, transport equation

One-dimensional random field Kac's model: localization of the phases

We study the typical profiles of a one dimensional random field Kac model, for values of the temperature and magnitude of the field in the region of the two absolute minima for the free energy of the corresponding random field Curie Weiss model. We show that, for a set of realizations of the random field of overwhelming probability, the localization of the two phases corresponding to the previous minima is completely determined. Namely, we are able to construct random intervals tagged with a sign, where typically, with respect to the infinite volume Gibbs measure, the profile is rigid and takes, according to the sign, one of the two values corresponding to the previous minima. Moreover, we characterize the transition from one phase to the other

Perfect simulation of infinite range Gibbs measures and coupling with their finite range approximations

In this paper we address the questions of perfectly sampling a Gibbs measure with infinite range interactions and of perfectly sampling the measure together with its finite range approximations. We solve these questions by introducing a perfect simulation algorithm for the measure and for the coupled measures. The algorithm works for general Gibbsian interaction under requirements on the tails of the interaction. As a consequence we obtain an upper bound for the error we make when sampling from a finite range approximation instead of the true infinite range measure