The present volume contains the texts of the invited talks delivered at the Sixth International Conference on Recent Progress in Many-Body Theories held in Arad, Israel during the period November 5-10 1989. The host institute was the Physics Department at the Ben Gurion University of the Negev. Beside the invited talks there have been also two poster sessions. The general format and style of the meeting followed closely those which had preceded it and evolved from the earlier conferences in the series: Trieste 1978, Oxtapec 1981, Altenberg 1983, San Francisco 1985 and Oulu 1987. The conferences in this series are intended to cover the broad spectrum of modem physics related to the many body problem. It starts on the smallest length scales in dealing with quark gluon plasmas and ends on the largest length scales in tackling many body problems in astrophysics. In between, it is concerned with nuclear physics, solid state physics, statistical mechanics, field theory, molecular dynamics, hydrodynamics, chaos, etc. Like in the Oulu conference, special emphasis has been put on recent developments in high Tc superconductivity. Beside the half day session devoted to it we have also organized an evening round table discussion on the future of the whole subject. Furthermore, a new, and in the opinion of the editor a very refreshing element which was absent in earlier conferences was the presentation of a few talks by experimentalists.

Section I: High Tc Superconductivity.- Flux Phases in the t-J Model.- Two Dimensional Phenomena in High Tc Superconductors.- Novel Singular Solutions of BCS Theory.- Magnetism and Superconductivity in Doped Lamellar Copper Oxide Systems.- A Vortex Lattice of Anyons in Strongly Correlated Systems.- Electron-Hole Liquid Model for High Tc Superconductivity.- Strong Electron Correlations in CuO2 Planes of High Temperature Superconductors.- Two Component Superconductivity.- Section II: Localization.- Coherent Back Scattering and Other Optical Effects in Random Media.- Many Body Techniques for Wave Propagating in Random Media.- Localization and Folding of Random Chains.- Section III: Nuclear Physics.- A New Theory of Collisions.- Calculations of the Ground State of 16O.- A New State of Nuclear Matter.- The "Ideal" Shell Model Calculation.- Non-Spurious Harmonic Oscillator States for Many-Body Systems.- Section IV: Microscopic Approaches I.- Inhomogeneous Quantum Liquids: Many Body Theory on the Testbench.- Coupled Cluster Parametrizations of Model Field Theories and their Bargman-Space Representations.- Fermion Monte Carlo Algorithms for Quantum Fluids.- Bose Condensate in Superfluid 4He and Momentum Distributions by Deep Inelastic Scattering.- Section V: Mesoscopic Systems.- Ballistic Electronic Transport in Semiconductor Structures.- Random-Matrix-Model for Fluctuations in Microscopic and Mesoscopic Systems.- Section VI: Strongly Correlated Systems.- Super-Effective-Field CAM Theory of Strongly Correlated Electron and Spin Systems.- Unified Description of Strongly and Weakly Correlated Electrons.- Fermi Hyper-Netted Chain Theory on a Lattice: The Hubbard Model.- Many Body Methods Applied to Scattering of Composite Particles in Gauge Theory with Confinement.- Section VII Microscopic Approaches Ii.- Two-Body Density Matrix for Quantum Fluids.- New Microscopic Description of Liquid 3He.- Excitation Spectrum of a 3He Impurity in 4He.- Section VIII: Feenberg Medal Presentation And Summary.- Achievements in Quantum Monte Carlo.- Summary of The VI International Conference on Recent Progress in Many Body Theories Arad Israel.