Professor Pechukas is being supported by the Theoretical and Computational Chemistry Program. His research will focus on three problems of many-body quantum dynamics: the problem of computing the dynamics efficiently and with accuracy, the problem of generalizing quantum rate theory to accommodate complex kinetic processes with randomly fluctuating activation barriers, and the problem of devising and analyzing simple soluble models for many-body quantum dynamics to illuminate a number of obscure issues in the theory of open systems. Specific areas of interest are to further develop and test his phase space path integral Monte Carlo method for real-time quantum dynamics, based on a compact `Fourier` expansion of wavefunctions in coherent states. Another aspect of this research will push the fluctuating barrier problem beyond the simplest case--classical Kramers problem in the spatial diffusion limit, barrier fluctuations driven by an external stochastic process--to which this work and that of others has so far been restricted. In a third aspect this research will explore a simple collision model recently devised for quantum Brownian motion, to answer questions about initial state preparation and long-time Markovian dynamics in open systems that interact strongly with their surroundings. The motivation for all three projects is the same. Chemistry is fundamentally quantum-mechanical and typically complex. Chemical processes in complex systems--charge separation in photosynthesis, oxygen fixation at the active site in thermally fluctuating hemoglobin, hydrogenation of carbonmonoxide at metal surfaces in synthetic fuel production--these are fundamentally quantum-mechanical processes involving many atoms simultaneously. To describe and to simulate complex chemical processes properly is fundamentally to study quantum dynamics in many-body systems.
