Introduction to Mathematical Physics/Statistical physics/Introduction

Statistical physics goal is to describe matter's properties at macroscopic scale from a microscopic description (atoms, molecules, etc\dots). The great number of particles constituting a macroscopic system justifies a probabilistic description of the system. Quantum mechanics (see chapter ---chapmq---) allows to describe part of systems made by a large number of particles: Schr\"odinger equation provides the various accessible states as well as their associated energy. Statistical physics allows to evaluate occupation probabilities $$P_l$$ of a quantum state $$l$$. It introduces fundamental concepts as temperature, heat\dots

Obtaining of probability $$P_l$$ is done using the statistical physics principle that states that physical systems tend to go to a state of ``maximum disorder'',. A disorder measure is given by the statistical entropy \index{entropy}

The statistical physics principle can be enounced as: