Open Problems In Strongly Correlated Electron Systems

Proceedings of the NATO Advanced Research Workshop, Bled, Slovenia, 26-30 April 2000

This is the second in a series of miniworkshops and Adriatico conferences devoted to the exciting field of strongly correlated electron systems including quantum Hall effect, metal insulator transition, heavy fermions and high Tc superconductivity. In spite of enormous efforts made by physicists worldwide to solve these difficult problems, many important issues are still widely open and this topic remains the most active field in condensed matter physics. The review talks and reports on original research given by the experts in the field represent a state-of-the-art summary of this fast-moving field.

Systems of strongly correlated electrons are at the heart of recent developments in condensed matter theory. They have applications to phenomena like high-c superconductivity and the fractional quantum hall effect. Analytical solutions to such models, though mainly limited to one spatial dimension, provide a complete and unambiguous picture of the dynamics involved. This volume is devoted to such solutions obtained using the Bethe Ansatz, and concentrates on the most important of such models, the Hubbard model. The reprints are complemented by reviews at the start of each chapter and an extensive bibliography.

Focusing on the purely theoretical aspects of strongly correlated electrons, this volume brings together a variety of approaches to models of the Hubbard type - i.e., problems where both localized and delocalized elements are present in low dimensions. The chapters are arranged in three parts. The first part deals with two of the most widely used numerical methods in strongly correlated electrons, the density matrix renormalization group and the quantum Monte Carlo method. The second part covers Lagrangian, Functional Integral, Renormalization Group, Conformal, and Bosonization methods that can be applied to one-dimensional or weakly coupled chains. The third part considers functional derivatives, mean-field, self-consistent methods, slave-bosons, and extensions.

This volume contains invited and contributed papers of eminent scientists who are deeply involved in the field of strongly correlated electron systems and high-Tc superconductivity. The topics of the papers include the Hubbard model, the t-J model, the polaronic model for high-Tc superconductivity, Fermi liquid and non-Fermi liquid theory, and heavy fermion systems.