Quantum Matter Lecture 17

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welcome back this lecture will be on Landau Fermi liquid theory this is the last examinable topic of the course after this we move on to BCS theory of superconductivity which is very interesting but it not examinable so land up from a liquid theory is basically the study of strongly interacting fermions we studied interacting fermions in the last few lectures and everything we done has really been based on the theory of very weakly interacting fermions so for example we started with first order perturbation theory and that my definition is accurate only to first order in the perturbation or really you comparing the energy of the perturbation the interaction to the to the Fermi energy which is the other scale in the system but also hartree fock and RP a are approximations that work very well for weakly interacting fermions but do not work well for a strongly interacting fermions typically however the physical systems that were usually interested in as condensed matter physicists usually have very strong interactions between the fermions so the interaction energy II interaction is typically larger or at least approximately equal to the other scale in the system which is the Fermi