The borderline of quantum electrodynamics and quantum optics offer spectacular results and problems concerning the foundations of radiation theory. Perhaps the major new viewpoint that has emerged from recent investigations is that one can now work inside a time-dependent quantum process, whereas up to now all elementary quantum processes were either stationary, or one worked with asymptotic in-and out-states, i.e. an S-matrix approach. In the-rirst part of this volume, the Quantum Electrodynamics, the present status of the main approaches to this most accurate of all physical theories are discussed: the Hamiltonian approach, the Green's function approach with particular emphasis to bound state problems, and the newer, nonperturbative approach. The latest numerical results on radiative corrections, Lamb shifts and anomalous magnetic moments are reviewed with new results for high Z atoms. Also discussed are different theoretical interpretations of the radiative phenomena as due to quantized field vacuum fluctuations or due to self energy. A small group of contributions are devoted to the physics and mathematical description of decaying or unstable states in quantum theory. This remarkable phenomenon of quantum theory still needs complete clarification, it is a time-dependent phenomenon, which can be described also by asymptotic S-matrix methods, but with complex energies.

Inhalt
I. Quantum Electrodynamics.- Finite Boundary Effects in Quantum Electrodynamics.- Nonperturbative Quantum Electrodynamics of Bound States and Radiative Processes.- Mass and Charge Renormalization in Quantum Electrodynamics.- Simple Physical Pictures for Radiative Processes: Vacuum Polarization versus Radiation Reaction (Abstract).- The Hamiltonian of Quantum Electrodynamics.- Nonperturbative Methods in Bound State Quantum Electrodynamics.- Recent Advances in Muonium Hyperfine Splitting Calculations.- II. Quantum Optics.- Chaos in Radiative Interactions.- Electron Spectrum and the Time-dependence of Initial State Population in a Model for Laser Induced Autoionization.- Cooperative Effects in One Dimension.- Theory of Time-Dependent Spectral Observations in QED and Quantum Optics.- Keldysh Approximation Revisited.- Coherence and Saturation in Strong Field Ionization.- Quantum Fluctuations as Corrections to Slowely Varying Quantities.- Radiation Interaction of Rydberg Atoms.- The Role of Scalar Product and Wigner Distribution in Optical and Quantum Mechanical Measurements.- Configuration Interaction in Multiphoton Ionization.- III. Decaying States.- Nonlinear Wave Equation for Decaying States.- Interference Phenomena in Unstable States.- Nonperturbative Treatment of Decaying States.- IV. Gauge Invariance.- $$\vec A.\vec por\vec r.\vec E?.$$ Minimal Coupling and Multipolar Hamiltonians in the Quantum Theory of Radiation.- Manifest Gauge Invariance in Nonrelativistic Quantum Mechanics with Classical Electromagnetic Fields.- Consequences of High Field Intensity in Semiclassical Electrodynamics.- Interaction Hamiltonian n Quantum Optics. Or: $$\vec p \cdot \vec Avs.\vec E \cdot \vec r$$ Revisited.- V. Quantum Correlations.- Is Reality Really Real? An Introduction toBell's Inequalities.- Bell's Theorem and Quasiclassical Quantum Distribution Theory: A Calculational Example.