Statistical Physics

A macroscopic system consists of "elementary objects" or "particles". We can approximate at macroscopic system dividing it into size subsystems smaller and smaller. The properties of the subsystems are identical to those of the of the starting system until we arrived at a certain size where these properties change, at this point we have reached a microscopic scale. There are several microscopic scales: If we study the properties of water we can consider a "particle" of water as molecule and may not be interested in the fact that dividing the molecule we find atoms, and so on. Our "particles" are described by attributes that "summarize" everything that occurs on a microscopic scale. Let's assume that these proprieties are well defined. The problem is to describe the properties of the macroscopic system from the properties of these "particles" and their interactions. Each microscopic scale has dimensions, times, energies, "particles" and characteristic interactions. It is possible to follow step by step the changes of each of the vary chosen scale and give consistency the explanation of the macroscopic behavior. Whether classical or quantum, the microscopic states correspond to the detailed description of the complete set of particles that make up the system. For example, the microscopic states of a simple fluid are the phase space of the system: positions and velocity of the molecules. What experience teaches us is that the states of the macroscopic system are quite different from the microscopic. What we know is that thermodynamics identifies a class of states, called equilibrium states, that described by a few coordinates, completely determine the system state. The central idea is that macroscopic states are probability measures which can be defined on the space of microscopic states, measures which satisfy certain simple constraints. Furthermore, the macroscopic quantities are the expectations values. In the thermodynamic case the intuitive motivation is linked to the idea that in a certain time of the macroscopic system, many microscopic states are "visited" during the dynamic evolution, of the system so that what counts at the macro scale, is the frequency with which the various microscopic states are presented. This book presents a general but modern vision of some aspects of statistical physics, mostly from the thermodynamic point of view. It uses specifics applications, in several areas of physics to settle the ground for a medium/advanced reader. Book jacket.