Organized versus self-organized criticality in the abelian sandpile model

We define stabilizability of an infinite volume height configuration and of a probability measure on height configurations. We show that for high enough densities, a probability measure cannot be stabilized. We also show that in some sense the thermodynamic limit of the uniform measures on the recurrent configurations of the abelian sandpile model (ASM) is a maximal element of the set of stabilizable measures. In that sense the self-organized critical behavior of the ASM can be understood in terms of an ordinary transition between stabilizable and non-stabilizableComment: 17 pages, appeared in Markov Processes and Related Fields 200

Weak coupling limits in a stochastic model of heat conduction

We study the Brownian momentum process, a model of heat conduction, weakly coupled to heat baths. In two different settings of weak coupling to the heat baths, we study the non-equilibrium steady state and its proximity to the local equilibrium measure in terms of the strength of coupling. For three and four site systems, we obtain the two-point correlation function and show it is generically not multilinear.Comment: 18 page

Loss without recovery of Gibbsianness during diffusion of continuous spins

We consider a specific continuous-spin Gibbs distribution $\mu_{t=0}$ for a double-well potential that allows for ferromagnetic ordering. We study the time-evolution of this initial measure under independent diffusions. For `high temperature' initial measures we prove that the time-evoved measure $\mu_{t}$ is Gibbsian for all $t$. For `low temperature' initial measures we prove that $\mu_t$ stays Gibbsian for small enough times $t$, but loses its Gibbsian character for large enough $t$. In contrast to the analogous situation for discrete-spin Gibbs measures, there is no recovery of the Gibbs property for large $t$ in the presence of a non-vanishing external magnetic field. All of our results hold for any dimension $d\geq 2$. This example suggests more generally that time-evolved continuous-spin models tend to be non-Gibbsian more easily than their discrete-spin counterparts

Large deviations for quantum spin systems

We consider high temperature KMS states for quantum spin systems on a lattice. We prove a large deviation principle for the distribution of empirical averages $\frac{1}{|\Lambda|} \sum_{i\in\Lambda} X_i$, where the $X_i$'s are copies of a self-adjoint element $X$ (level one large deviations). From the analyticity of the generating function, we obtain the central limit theorem. We generalize to a level two large deviation principle for the distribution of $\frac{1}{|\Lambda|}\sum_{i\in\Lambda} \delta_{X_i}$.Comment: 22 page

Testing the irreversibility of a Gibbsian process via hitting and return times

We introduce estimators for the entropy production of a Gibbsian process based on the observation of a single or two typical trajectories. These estimators are built with adequate hitting and return times. We then study their convergence and fluctuation properties. This provides statisticals test for the irreversibility of Gibbsian processes.Comment: 16 pages; Corrected version; To appear in Nonlinearit