Recent advances in Stellar Pulsation Theory

(1) Using a grid of 1-D radiation hydrodynamic models of Cepheids and RR Lyraes, we have used modern machine learning methods to develop relations connecting quantitative measures of light curve structure and period    to global stellar parameters like Mass, Luminosity and Effective Temperature. We apply these relations to OGLE IV data for the LMC and SMC and find distance moduli that are consistent with the literature. We discuss future implications.

(2) We use 1-D radiation hydrodynamic models of Cepheids/RR Lyraes/Type II Cepheids to study the radiation hydrodynamics of the stellar photosphere/hydrogen ionization front interaction and hence provide a plausible explanation of observed properties of the Period-Color relations in these different types of variable stars. We discuss future implications.