This volume contains all of the invited lectures presented at the NATO ARWon "New Methods in Quantum Theory" held in Halkidiki, Greece from May 14th to May 19th, 1995. This survey of new perspectives, techniques and results in quantum theory contains 26 chapters by leading quantum chemists and physicists from 14 countries. The book covers a wide range of topics, though the emphasis throughout is on new approaches and their interrelationships. Topics covered include dimensional scaling, the hyperspherical method applied both to reactive scattering theory and to bound state problems, chaotic behaviour, large-order perturbation theory, complex eigenvalues and quasistationary states, semiclassical methods, cusps in hyperaccurate wave functions, density functional theory, relativistic quantum theory, and quantum Monte Carlo methods. I hope very much that the various lectures presented at this Advanced Research Workshop will be of as great interest to the reader as they were to the participants. The organization of the ARW would have been impossible without the generous funding by NATO, which is gratefully acknowledged. I sincerely thank Drs. J. -M. Cadiou, Assistant Secretary General for Scientific and Environmental Affairs, and J. A. Rausell-Colom, Programme Director for Priority Area on High Technology, North Atlantic Treaty Organization, who helped me throughout the various stages of the ARW.

Table of Contents:
DIMENSIONAL SCALING.- SUBHAMILTONIAN METHODS.- DIMENSIONAL RENORMALIZATION FOR ELECTRONIC STRUCTURE CALCULATIONS.- GENERALIZED SELF-CONSISTENT-FIELD APPROXIMATIONS.- DIMENSIONAL EXPANSIONS FOR ATOMIC SYSTEMS.- THE MANIFESTATION OF CHAOTIC BEHAVIOUR OF THE HYDROGEN ATOM IN THE PRESENCE OF UNIFORM ELECTRIC FIELD.- MULTIELECTRON, MULTICHANNEL PROBLEMS AND THEIR SOLUTION TO ALL-ORDERS VIA THE DIAGONALIZATION OF STATE-SPECIFIC COMPLEX EIGENVALUE SCHRÖDINGER EQUATIONS.- LARGE ORDERS OF 1/n-EXPANSION IN QUANTUM MECHANICS AND ATOMIC PHYSICS.- SIZE-EXTENSIVE BRILLOUIN-WIGNER PERTURBATION THEORY. SIZE-EXTENSIVE BRILLOUIN-WIGNER COUPLED CLUSTER THEORY.- LEAST MOTION, HYPERSPHERICAL COORDINATES, AND POLYTOPES.- EVOLUTION OF ATOM-MOLECULAR EIGENSTATES.- HYPERANGULAR MOMENTUM: APPLICATIONS TO ATOMIC AND MOLECULAR SCIENCE.- QUANTUM AND SEMI-CLASSICAL METHODS IN REACTIVE SCATTERING.- MULTIDIMENSIONAL ANGULAR FUNCTION METHODS IN THEORETICAL AND APPLIED PHYSICS.- HYPERSPHERICAL STURMIAN BASIS FUNCTIONS IN RECIPROCAL SPACE.- INELASTIC SCATTERING WITH COULOMB FORCES: A SEMICLASSICAL S-MATRIX APPROACH.- CUSP CONDITIONS AND ELECTRON CORRELATION.- LOCAL-SCALING MANY-ELECTRON DENSITY FUNCTIONAL THEORY.- DENSITY FUNCTIONAL THEORY: IMPROVING THE FUNCTIONALS, EXTENDING THE APPLICATIONS.- ELECTRON CORRELATION AND THE STRUCTURE OF THE EXCHANGE-CORRELATION POTENTIAL AND THE CORRELATION ENERGY DENSITY IN DENSITY FUNCTIONAL THEORY.- RELATIVISTIC PSEUDOPOTENTIALS AND NONLOCAL EFFECTS.- ONE CENTER EXPANSION IN QUANTUM MECHANICAL MOLECULAR CALCULATIONS.- DISTRIBUTED GAUSSIAN BASIS SETS: SOME RECENT RESULTS AND PROSPECTS.- EXACT AB INITIO QUANTUM CHEMISTRY.- COMMENTS ON COMPUTATIONAL CHEMISTRY, IN GENERAL AND QUANTUM CHEMISTRY, IN PARTICULAR.- HYPERSPHERICAL COORDINATES IN REACTIVE SCATTERING THEORY.-CONTRIBUTORS.