Results 1  10
of
13
The spectral gap for a Glaubertype dynamics in a continuous gas
, 2000
"... . We consider a continuous gas in a d dimensional rectangular box with a nite range, positive pair potential, and we construct a Markov process in which particles appear and disappear with appropriate rates so that the process is reversible w.r.t. the Gibbs measure. If the thermodynamical paramenter ..."
Abstract

Cited by 38 (6 self)
 Add to MetaCart
. We consider a continuous gas in a d dimensional rectangular box with a nite range, positive pair potential, and we construct a Markov process in which particles appear and disappear with appropriate rates so that the process is reversible w.r.t. the Gibbs measure. If the thermodynamical paramenters are such that the Gibbs specication satises a certain mixing condition, then the spectral gap of the generator is strictly positive uniformly in the volume and boundary condition. The required mixing condition holds if, for instance, there is a convergent cluster expansion. Key Words: Spectral gap, Gibbs measures, continuous systems, birth and death processes Mathematics Subject Classication: 82C21, 60K35, 82C22, 60J75 This work was partially supported by GNAFA and by \Conanziamento Murst" v1.4 1. Introduction We consider a continuous gas in a bounded volume R d , distributed according the Gibbs probability measure associated to a nite range pair potential '. The Gibbs measu...
Quasifactorization of the entropy and logarithmic Sobolev inequalities for Gibbs random fields
 2001 Probab. Theory Rel. Fields 120 569–84
"... ..."
Cédric: A TwoScale Proof of a Logarithmic Sobolev Inequality
"... We consider an N–site lattice system with continuous spin variables governed by a Ginzburg–Landau–type potential. Because we are interested in the Kawasaki dynamics, we work with the canonical ensemble in which the mean m is given. We prove a logarithmic Sobolev inequality (LSI) which is uniform in ..."
Abstract

Cited by 9 (1 self)
 Add to MetaCart
We consider an N–site lattice system with continuous spin variables governed by a Ginzburg–Landau–type potential. Because we are interested in the Kawasaki dynamics, we work with the canonical ensemble in which the mean m is given. We prove a logarithmic Sobolev inequality (LSI) which is uniform in m and has the optimal scaling in the system size N. The method involves a two–scale “block–spin ” decomposition. Choosing sufficiently large blocks leads to convexification of the coarse–grained Hamiltonian; consequently, the Bakry–Emery principle implies a macroscopic LSI. On the other hand, the Holley–Stroock lemma implies a microscopic LSI as long as the block–spin size is bounded. We show that the macro – and microscopic LSI can be combined to yield a global LSI. The main ingredient in this final step is the Talagrand inequality.
On Decay of Correlations for Unbounded Spin Systems with Arbitrary Boundary Conditions
, 2001
"... We propose a method based on cluster expansion to study the truncated correlations of unbounded spin systems uniformly in the boundary condition and in a possible external field. By this method we study the spinspin truncated correlations of various systems, including the case of infinite range sim ..."
Abstract

Cited by 6 (0 self)
 Add to MetaCart
We propose a method based on cluster expansion to study the truncated correlations of unbounded spin systems uniformly in the boundary condition and in a possible external field. By this method we study the spinspin truncated correlations of various systems, including the case of infinite range simply integrable interactions, and we show how suitable boundary conditions and/or external fields may improve the decay of the correlations. x0. Introduction In recent times a considerable effort has been spent to generalize the classical framework of the complete analiticity for bounded spin systems to the unbounded case. This effort is motivated by the fact that, both in the bounded and in unbounded case, it is in general difficult to prove directly the logSobolev inequality, which ensures the complete analyticity, or the existence of a spectral gap for the spin systems, while it is possible to prove the equivalence of the existence of the spectral gap with some other property of the syst...
Correlation at Low Temperature: I. Exponential Decay
"... The present paper generalizes the analysis [18, 2] of the correlations for a lattice system of realvalued spins at low temperature. The Gibbs measure is assumed to be generated by a fairly general pair potential (Hamiltonian function). The novelty, as compared to [18, 2], is that the singlesite (s ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
The present paper generalizes the analysis [18, 2] of the correlations for a lattice system of realvalued spins at low temperature. The Gibbs measure is assumed to be generated by a fairly general pair potential (Hamiltonian function). The novelty, as compared to [18, 2], is that the singlesite (self) energies of the spins are not required to have only a single local minimum and no other extrema. Our derivation of exponential decay of correlations goes through the spectral analysis of a deformed Laplacian closely related to the Witten Laplacian studied in [18, 2]. We prove that this Laplacian has a spectral gap above zero and argue that this implies exponential decay of the correlations.
A twoscale approach to logarithmic Sobolev inequalities and the hydrodynamic limit
, 2008
"... We consider the coarsegraining of a lattice system with continuous spin variable. In the first part, two abstract results are established: sufficient conditions for a logarithmic Sobolev inequality with constants independent of the dimension (Theorem 3) and sufficient conditions for convergence to ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
We consider the coarsegraining of a lattice system with continuous spin variable. In the first part, two abstract results are established: sufficient conditions for a logarithmic Sobolev inequality with constants independent of the dimension (Theorem 3) and sufficient conditions for convergence to the hydrodynamic limit (Theorem 8). In the second part, we use the abstract results to treat a specific example, namely the Kawasaki dynamics with Ginzburg–
Properties of Isoperimetric, Functional and TransportEntropy Inequalities Via Concentration
, 2009
"... Various properties of isoperimetric, functional, TransportEntropy and concentration inequalities are studied on a Riemannian manifold equipped with a measure, whose generalized Ricci curvature is bounded from below. First, stability of these inequalities with respect to perturbation of the measure ..."
Abstract
 Add to MetaCart
(Show Context)
Various properties of isoperimetric, functional, TransportEntropy and concentration inequalities are studied on a Riemannian manifold equipped with a measure, whose generalized Ricci curvature is bounded from below. First, stability of these inequalities with respect to perturbation of the measure is obtained. The extent of the perturbation is measured using several different distances between perturbed and original measure, such as a onesided L ∞ bound on the ratio between their densities, Wasserstein distances, and KullbackLeibler divergence. In particular, an extension of the Holley–Stroock perturbation lemma for the logSobolev inequality is obtained. Second, the equivalence of TransportEntropy inequalities with different cost functions is verified, by obtaining a reverse Jensen type inequality. In view of a recent result of Gozlan, this is used to obtain tensorization properties of concentration inequalities with respect to various productmetrics, and the tensorization result for isoperimetric inequalities of Barthe–Cattiaux–Roberto is easily recovered. Some further applications are also described. The main tool used is a previous precise result on the equivalence between concentration and isoperimetric inequalities in the described setting.
Summary
"... When interpreting an image, a human observer takes into account not only the external input given by the intensity or color information in the image, but also internally represented knowledge. The present work is devoted to modeling such an interaction by combining in a segmentation process lowleve ..."
Abstract
 Add to MetaCart
(Show Context)
When interpreting an image, a human observer takes into account not only the external input given by the intensity or color information in the image, but also internally represented knowledge. The present work is devoted to modeling such an interaction by combining in a segmentation process lowlevel image cues and statistically encoded prior knowledge about the shape of expected objects. To this end, we introduce the diffusion snake as a variational method for image segmentation. It is a hybrid model which combines the external energy of the MumfordShah functional with the internal energy of the snake. Minimization by gradient descent results in an evolution of an explicitly parametrized contour which aims at maximizing the lowlevel homogeneity in disjoint regions. In particular, we present an extension of the MumfordShah functional which aims at maximizing the homogeneity with respect to the motion estimated in each region. We named the proposed variational method motion competition, because neighboring regions compete for the evolving contour in terms of their motion homogeneity. Minimization of the proposed functional
Journal of Functional Analysis 243 (2007) 121157.
"... A new criterion for the logarithmic Sobolev inequality and two applications PREPRINT of article published in ..."
Abstract
 Add to MetaCart
A new criterion for the logarithmic Sobolev inequality and two applications PREPRINT of article published in