Nucleation in Quantum Liquids

In order to understand how nucleation proceeds in quantum liquids such as 4He and 3He, and the peculiarities of such quantum systems, I present a review of nucleation in condensed matter. By describing successive experiments, I first illustrate the interest and use of the elementary "standard theory" of nucleation. Then I consider its limitations and the existence of "spinodal" and instability limits, possibly in the frame of "density functional" methods. When finally discussing nucleation at low temperature, I consider a further improvement of the standard theory, namely the possibility of nucleation by quantum tunneling. The main emphasis is on crystallization and cavitation in liquid helium, but I also consider water, liquid hydrogen, wetting, the nucleation of steps on crystal surfaces, vortices etc.