Contents: Introduction; problems equivalent to the analysis of suitable functional integrals: critical point and field theory; Other functional integrals: Fermi sphere and Bose condensation; Effective potentials and Schwinger equation; Multiscale decomposition of propagators and fiels: running effective potentials; Asymptotic freedom: upper critical dimension; Beyond the linear approximations: The Beta function and perturbation theory; The Beta function as dynamical system: Asymptotic freedom and marginal theories; Anomalus dimension; The Fermi liquid and the Luttinger Model; The Generic Critical point for d=3,y=0; the e-expansion; Bose Condensation reformulation; Bose Consensation: Effective potentials; The Beta function for the Bose Condensation; A brief hystorical note. |