Behavior of Large Random Systems

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9419362 Deutsch Research is proposed in three areas of theoretical statistical physics. (1) Studies of nonequilibrium processes which possess large fluctuations. The objective is to better understand the structures which arise in fully developed turbulence by using a simulation technique that selects large, but unlikely fluctuations. The results should provide an improved understanding of turbulent intermittency. (2) Structural prediction for macromolecules. Prediction of structure and morphology is important in the understanding of materials and biomaterials, but requires knowing the forces between the individual building blocks of the systems. The large experimental data base on protein structure will be used to systematically determine the force field that acts between different atoms or constituent submolecules. The results will be important in determining structures of macromolecules. (3) Quantum simulations using statistical methods. A large class of problems is difficult to simulate due to sign changes during averaging processes. This class of problems is of fundamental and current interest. A method will be studied which greatly speeds up this averaging process by replacing the sudden change in sign by a continuously varying phase. The consideration of the statistics of these phases leads to improved methods for doing these averages. %%% Theoretical research involving advanced computational techniques will be done on a variety of problems dealing with very large random systems. One problem will develop new methods to better determine the structure of biologically important macromolecules. Another project will deal with new algorithms to surmount a fundamental problem involving calculations of physical systems of interacting electrons. The solution of this problem can have a profound impact on calculations for high temperature superconductors. Finally, calculations will be made on the effect of rare fluctuations on the development of turbulence in fluids. Turbulence is an extremely difficult problem to understand and it affects a wide variety of everyday happenings. ***