This book is a remarkable synthesis, a clear and simple introduction to Quantum Physics with a sort of Galilean dialogue on the supreme systems of contemporary Physics. The author, whose research interests and work extended from quarks to liquid systems and from crystals to stars, introduces the common conceptual and mathematical framework of all quantum theories, realistic enough to successfully confront Nature: Quantum Field Theory applied to the study of both dilute and condensed matter. In the dilute limit, quantum mechanics is shown to be a good approximation to Quantum Field Theory. However, in condensed matter physics the problem of the ground state, which acts as a kind of template for physical reality, is studied under the hypothesis that the standard perturbative vacuum is unstable with respect to a new coherent vacuum, whose spectrum emerges quite naturally through a simple variational procedure.

Up until now the dominant view of condensed matter physics has been that of an "electrostatic MECCANO" (erector set, for Americans). This book is the first systematic attempt to consider the full quantum-electrodynamical interaction (QED), thus greatly enriching the possible dynamical mechanisms that operate in the construction of the wonderful variety of condensed matter systems, including life itself.A new paradigm is emerging, replacing the "electrostatic MECCANO" with an "electrodynamic NETWORK," which builds condensed matter through the long range (as opposed to the "short range" nature of the usual electrostatic forces) electrodynamical interaction; this interaction creates "coherent configurations" of the elementary systems (atoms and molecules), which oscillate in phase with a coherent macroscopic (and classical) electromagnetic field that, through the strong interaction with matter, remains trapped inside it.