ABSTRACT
This chapter is concerned with the low-temperature behavior of systems of many particles and with the third law of thermodynamics. In common with the other laws of thermodynamics, the third law is based on observation. All of the evidence shows that the third law cannot be violated. Before concluding this chapter, the authors give a brief introduction to an important topic in astrophysics which is concerned with the thermal properties of black holes. In considering the application of the zeroth law and the third law to black holes, it is instructive to introduce the surface gravity, which is the gravitational acceleration of a mass at the event horizon as measured by a distant observer. Because the entropy of a black hole does not tend to zero or to a constant value with decreasing temperature, it is necessary to modify the statement of the third law when applied to black holes.
