ABSTRACT
This chapter presents a completely different approach developed by L. D. Landau for Fermi liquids which provides exact relations between certain observable quantities. It describes the basic assumptions of the theory in a heuristic and phenomenological manner. The chapter shows how to calculate thermodynamical observables with the set of assumptions and also presents the microscopic justification of the theory. In practical microscopic calculations of the Landau parameters, one typically performs infinite summations of diagrams. Attempts have been made to calculate Landau parameters both in liquid helium and in nuclear matter. The domain of validity of the Landau theory is restricted to phenomena which involve excitations very close to the Fermi surface. A normal Fermi liquid is defined as a system in which the non-interacting ground state evolves into the interacting ground state and there is a one-to-one correspondence between the bare particle states of the original system and the dressed or quasiparticle states of the interacting system.
