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Basic Theoretical Physics: A Concise Overview P30. This concise treatment embraces, in four parts, all the main aspects of theoretical physics (I . Mechanics and Basic Relativity, II. Electrodynamics and Aspects of Optics, III. Non-relativistic Quantum Mechanics, IV. Thermodynamics and Statistical Physics). It summarizes the material that every graduate student, physicist working in industry, or physics teacher should master during his or her degree course. It thus serves both as an excellent revision and preparation tool, and as a convenient reference source, covering the whole of theoretical physics. It may also be successfully employed to deepen its readers’ insight and. | Part IV Thermodynamics and Statistical Physics 39 Introduction and Overview to Part IV This is the last course in our compendium on theoretical physics. In Thermodynamics and Statistical Physics we shall make use of a classical non-relativistic mechanics as well as b non-relativistic quantum mechanics and c aspects of special relativity. Whereas in the three above-mentioned subjects one normally deals with just a few degrees of freedom i.e. the number of atoms N in the system is usually 1 or of the order of magnitude of 1 in thermodynamics and statistical physics N is typically 1023 i.e. the number of atoms and hence degrees of freedom in a volume of 1 cm3 of a gas or liquid under normal conditions is extremely large. Microscopic properties are however mostly unimportant with regard to the collective behavior of the system and for a gas or liquid only a few macroscopic properties such as pressure p temperature T and density p characterize the behavior. Quantum mechanics usually also deals with a small number of degrees of freedom however with operator properties which lead to the possibility of discrete energy levels. In addition the Pauli principle becomes very important as soon as we are dealing with a large number of identical particles see below . In classical mechanics and non-relativistic quantum mechanics we have v2 C c2 with typical atomic velocities of the order of c KVWI However statistical physics also includes the behavior of a photon gas for example with particles of speed c. Here of course special relativity has to be taken into account see Part I 1. In that case too the relevant macroscopic degrees of freedom can be described by a finite number of thermodynamic potentials e.g. for a photon gas by the internal energy U T V N and entropy S T V N or by a single combination of both quantities the Helmholtz free energy F T V N U T V N - T S T V N where T is the thermodynamic temperature of the system in degrees Kelvin K V the volume and N the number of .
