Errico Presutti – författare

In this volume a theory for models of transport in the presence of a free boundary is developed.Macroscopic laws of transport are described by PDE's. When the system is open, there are several mechanisms to couple the system with the external forces. Here a class of systems where the interaction with the exterior takes place in correspondence of a free boundary is considered. Both continuous and discrete models sharing the same structure are analysed. In Part I a free boundary problem related to the Stefan Problem is worked out in all details. For this model a new notion of relaxed solution is proposed for which global existence and uniqueness is proven. It is also shown that this is the hydrodynamic limit of the empirical mass density of the associated particle system. In Part II several other models are discussed. The expectation is that the results proved for the basic model extend to these other cases.All the models discussed in this volume have an interest in problems arising in several research fields such as heat conduction, queuing theory, propagation of fire, interface dynamics, population dynamics, evolution of biological systems with selection mechanisms.In general researchers interested in the relations between PDE’s and stochastic processes can find in this volume an extension of this correspondence to modern mathematical physics.

Entropy inequalities, correlation functions, couplingsbetween stochastic processes are powerful techniques whichhave been extensively used to give arigorous foundation tothe theory of complex, many component systems and to itsmany applications in a variety of fields as physics,biology, population dynamics, economics, ...The purpose of the book is to make theseand othermathematical methods accessible to readers with a limitedbackground in probability and physics by examining in detaila few models where the techniques emerge clearly, whileextra difficulties arekept to a minimum.Lanford's method and its extension to the hierarchy ofequations for the truncated correlation functions, thev-functions, are presented and applied to prove the validityof macroscopic equations forstochastic particle systemswhich are perturbations of the independent and of thesymmetric simple exclusion processes. Entropy inequalitiesare discussed in the frame of the Guo-Papanicolaou-Varadhantechnique and of theKipnis-Olla-Varadhan super exponentialestimates, with reference to zero-range models. Discretevelocity Boltzmann equations, reaction diffusionequations and non linear parabolic equations are considered,as limits of particles models. Phase separation phenomenaare discussed in the context of Glauber+Kawasaki evolutionsand reaction diffusion equations. Although the emphasis isonthe mathematical aspects, the physical motivations areexplained through theanalysis of the single models, withoutattempting, however to survey the entire subject ofhydrodynamical limits.

Collective behavior in systems with many components, blow-ups with emergence of microstructures are proofs of the double, continuum and atomistic, nature of macroscopic systems, an issue which has always intrigued scientists and philosophers. Modern technologies have made the question more actual and concrete with recent, remarkable progresses also from a mathematical point of view. The book focuses on the links connecting statistical and continuum mechanics and, starting from elementary introductions to both theories, it leads to actual research themes. Mathematical techniques and methods from probability, calculus of variations and PDE are discussed at length.