The Phase Structure of Quantum Field Systems -- Formulation of the Method -- The Phase Structure of the (?2)2 Field Theory in R1+1 -- The Phase Structure of the Three-Dimensional ?4 Theory -- The Four-Dimensional ?4 Theory -- The ?4 Theory at Finite Temperatures -- The Two-Dimensional Yukawa Theory -- The Gaussian Equivalent Representation of Functional Integrals in Quantum Physics -- Path Integrals in Quantum Physics -- The Gaussian Equivalent Representation of Functional Integrals -- The Polaron Problem -- The Character of the Phase Transition in Two- and Three-Dimensional ?4 Theory -- Wave Propagation in Randomly Distributed Media -- Bound States in QFT -- Oscillator Representation in Quantum Mechanics -- The Oscillator in Quantum Mechanics -- The Oscillator Representation in Rd -- The Oscillator Representation in the Space R3 -- Anharmonic Potentials -- Coulomb-Type Potentials -- The Relativized Schrödinger Equation -- Three-Body Coulomb Systems.

This book describes in detail the oscillator representation method and its application to an approximate solution of the Schrödinger equation with an appropriate interaction Hamiltonian. The method also works well in quantum field theory in the strong coupling regime in calculations of path integrals, as explained by the authors. Furthermore, spectral problems in quantum mechanics are treated. The book addresses students as well as researchers in quantum physics, quantum field theory, and nuclear and molecular physics.