The study of variable stars is basic to much of astronomy. The properties of the variability provide more information than can be obtained from static stars and they contribute greatly to our understanding of stellar structure and evolution, galactic evolution and cosmology. This project concerns modelling of stellar instability and understanding its systematics. A new nonlinear adaptive hydrodynamic code which produces better agreement between the models and the observations has been developed. This new method resolves and tracks the important physical features during the pulsation cycle. In this study, the results from the new code will be combined with the PI's previously developed semi-analytical theory of pulsation to gain insights into the mechanisms. The stars which will be considered range from the regularly varying Cepheids and RR Lyrae stars to the erratic RV Tauri stars and Semi-regular variables. The effects of stochastic noise on pulsations and methods of analysis of time-dependent signals will also be studied in the context of comparing the theoretical results with observation.
