# Physics 303a - Statistical Physics

### Prerequisite:

Physics 214 (Introductory Quantum Mechanics) or the equivalent

### Description:

A self-contained one-semester treatment of many particle systems using classical and quantum statistics to derive the laws of thermodynamics and to study the properties of macroscopic systems. The course includes applications to solid state physics, astrophysics, biological physics and other fields using both classical and quantum perspectives.

The subject of statistical mechanics is part of the core of physics. It is concerned with predicting the bulk properties of macroscopic matter, especially those affected by thermal energy, from microscopic principles. It provides a fundamental explanation of the laws of thermodynamics including the second law. It accounts for the behavior of photons and phonons (quantized sound waves), explains what happens to ideal gasses in the quantum limit, and accounts for the transformations of matter between different phases. Statistical physics explains what happens as the absolute zero of temperature is approached, explains the transport of heat and momentum, and provides insight into novel phenomena at the frontiers of physics, including the amazing Bose-Einstein condensation, the behavior of nuclear matter in stars, and other exciting developments involving many particle systems. Particle physics has consistently drawn key ideas from this field, which has intimate mathematical similarities to quantum field theory.

The central conceptual ideas in statistical physics include the laws of thermodynamics, especially the second law and the concept of entropy; the canonical probability distribution, which specifies how likely it is that a system at constant temperature will be found in a particular one of its many possible states; the partition function, from which all the thermodynamic properties of a system can be obtained; and the chemical potential, which allows one to understand diffusive equilibrium in a system whose particles can move around.

Chemistry has always been intimately related to statistical and thermal physics. In recent years, statistical physics has undergone an amazing expansion, so that it is now often used outside its traditional domain in biological physics, neural networks, information science and in "social" and "financial" physics—which use ideas originating in physics to interpret a wide variety of phenomena ranging from terrorist attacks to "black swan" (extraordinarily rare) events in the gyrations of stock prices.

### Background:

The background required for this course is modest. From quantum physics, you need to understand the existence of discrete energy eigenstates for bound systems and the concept of the de Broglie wavelength. From classical mechanics, you don?t need much more than introductory physics. The ideas of thermodynamics will be taught from scratch in the course. The mathematical level of the course is comparable to sophomore physics, i.e. multivariable calculus, but vector calculations are not usually needed.