The XIV International Workshop on Condensed Matter Theories has been held at the Elba International Physics Center (EIPC), Marciana Marina, Isola d'Elba, Italy, from 18-23 June, 1990. The Workshop started in 1977 in Sao Paolo, Brazil, as the 1st Pan American Workshop on Condensed Matter Theories, with the purpose of bringing together scientists from the Western countries, working in many different topics of Condensed Matter Theories, to facilitate exchanges of ideas and technologies from different areas as well as collaborations among the scientists. The next five Workshops were held at Trieste, Italy (1978), in Buenos Aires, Argentina ( 1979), in Caracas, Venezuela (1980), in Mexico City, Mexico (1981) and in St. Louis, Missouri, U. S. A. (1982). Given the international dimension reached by the Workshop, it was decided to extend it into an International Workshop, which was held for the first time in Altenberg, Germany (1983). The next editions took place in Granada, Spain (1984), San Francisco, California, U. S. A. (1985), Argonne, Illinois, U. S. A. (1986), Oulu, Finland (1987), Taxco, Mexico (1988) and Campos do Jordao, Brasil (1989). Many scientists have contributed to the development of the various editions of the Work shop. However, a particular mention has to be made to Profs. Manuel de Llano and Angel Plastino who initially proposed the Workshop and carried it forward, and to Prof. J . W. Clark, whose efforts have been of immense help to its recent developments.

I. Formal Methods.- Artificial Neural Networks that Learn Many-Body Physics.- Quantum Statistical Microdynamics and Critical Phenomena.- Quantum Spin Lattice Models: a Coupled-Cluster Treatment.- Time Dependent Mean Field Approximation in a Boson System.- Inhomogeneous Boson System Made Planar.- II. Quantum Fluids.- The Shape of Fluids.- Single Particle Properties of Atomic Deuterium.- Studies of the Critical Point of 4He.- The Spectral Function of Bose Superfluids: a Sum Rule Approach.- III. Electronic Systems, Atoms and Molecules.- Collective Spin Waves in Maxwellian Electron Plasma.- Test of Density Functional Approximation for an Atom in a Strong Magnetic Field.- Ionic Diffusion Phenomena in Superionic Conductors.- Electric Field Induced Solidification-Theory of Electro-Rheology Fluids.- Toward a Non-Born-Oppenheimer Density Functional Theory in the Context of Local-Scaling Transformations.- Bragg Intensities and Diffuse Scattering in Ag2Se: a Molecular Dynamics Study.- IV. High-Tc Superconductivity.- Dynamics of the Anderson Model for Dilute Magnetic Alloys: a Quantum Monte Carlo and Maximum Entropy Study.- High Temperature Superconductivity in an Exactly Solvable Model.- Cooper Pair Binding Energy and the BCS Gap Energy Revisited.- Coopers Pairs, Local Pairs, and TF-Scaled High-Tc Superconductivity.- Electron-Hole Liquid Model for High Tc-Superconductivity.- MEP Approach to the Anderson-Hubbard Model.- V. Lattice Theories.- Correlated Lattice Fermions in High Dimensions.- Cluster Gutzwiller Approximation.- The U(1)3 Lattice Gauge Vacuum.- Electronic Diamagnetism in Two-Dimensional Lattices.- Nuclear Physics and QCD.- Meson-Meson Scattering as a Many-Body Problem.- Alpha-Nucleus Interaction from an Inverse Scattering and Energy-Density Formalism.- Spin and Tensor Correlations in Model Nuclear Matter.- On Narrow ? Hypernuclear States with Positive Energy.- Electromagnetic Response in Nuclear Matter and Complex Nuclei.- Use of Correlated Hyperspherical Harmonic Basis for Strongly Interacting Systems.- Variational Cluster Methods in Coordinate Space for Small Systems: Center of Mass Corrections Made Easy.- Short-Range Correlations and Single-Particle Spectral Functions in Nuclear Matter.- Functional Techniques in the Many-Body Problem: the Longitudinal Nuclear Response function.- Contributors and Participants.