Topics in Statistical Physics

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Collective phenomena in condensed matter systems associated with quenched randomness and transport will be investigated. Phenomena to be studied include the effects of thermal fluctuations and pinning on eqilibrium and non-equilibrium behavior in Type-II superconductors in a magnetic field and statics and dynamics of spin glasses, random magnets and other systems such as cross-linked gels. All of these involve classical phase transitions in the presence of randomness and slow dynamics which result from a distribution of barrier heights. The statistical behavior of nonlinear collective transport phenomena such as the nonlinear dynamics of flux lines in superconductors, sliding charge density waves, fluids in porous media, sand piles and the motion of geologic faults will be studied with an emphasis on their universal features. The effects of randomness on low temperature quantum mechanical behavior of superfluids, superconductors, metals and spin systems will also be investigated. In particular, the nature of the zero temperature phase transitions, such as metal-insulator transitions, will be studied. %%% The study of the collective behavior of many-particle systems lies at the foundation of condensed matter, or solid state, physics. However, very few, if any, of these systems are perfect. To varying degrees all condensed matter systems have randomness associated with their properties. The proposed research will study the effects of randomness in a variety of specific systems of current interest, such as superconductors and magnets, to determine its effects on the system statics, dynamics and transport. This basic research will look for universal features which are common to these systems and thus provide a solid physical understanding of the behavior of a variety of condensed matter systems.