Numerical calculations of the structure and evolution of stars require a solid understanding of the hydrodynamic differential equations that underlie all gas dynamical processes. They also require knowledge of numerous additional physical processes, such as nuclear reactions, stellar opacities, and equations of state. The Principal Investigator proposes to focus on the latter two processes (Project 1). Furthermore, he will carry out numerical computations of stellar envelope pulsations using a nonlinear radiation hydrodynamics code (Project 2). Project 1 is designed to improve and to resolve present uncertainies in the opacity and equations of state tables used in stellar atmosphere studies. Success in this task is of crucial importance to Project 2, which will focus on stellar envelope pulsations, such as those observed in RR Lyrae and Cepheid stars. The work will be done in collaboration with large atomic physics groups at the University College London and Queen's University Belfast, and with colleagues in the US, France, Germany, and Venezuela.
