Focusing on many-body systems, the book explores collective phenomena in gases of bosons and fermions, highlighting oscillations in density driven by competing field variables. It delves into the intriguing dynamics of superfluid 3He, where molecular attractions lead to Cooper pairs, while short-range repulsion is countered by paramagnon oscillations. This interplay ultimately reveals the nature of superfluidity. The text employs a classical version of the Hubbard-Stratonovich transformation to analyze the competition among various channels effectively.
