5Phase transitions

II Statistical Physics

5 Phase transitions
In the remaining of the course, we are going to study phase transitions. This is
a discrete change in the properties of a system, characterized by discontinuities
in some of the variables describing the system. Macroscopically, these often
correspond to some rather drastic changes, such as freezing and boiling.
We have already met some examples of phase transitions before, such as
Bose–Einstein condensation. However, in this chapter, we are mainly going to
focus on two examples the liquid-gas transition, and the Ising model. At first
sight, these two examples should be rather unrelated to each other, but it turns
out they behave in a very similar way. In fact, it seems like all phase transitions
look somewhat alike. After examining these systems in some detail, our goal is
to understand where this similarity came from.