Screening of Thermonuclear Reaction Rates

This subject has received a lot of attention lately because of uncertainty in how to extend the usual methods to describe screening of nuclear reactions in cold, dense (strongly coupled) matter. It is a major source of uncertainty in describing the explosions of white dwarfs as type Ia supernovae, and those in the crusts of neutron stars that may cause superbursts. Recent terrestrial experiments indicating anomalously high levels of screening when low-energy deuteron beams collide with highly deuterated metal targets give further evidence that we have more to learn about screening. I will begin by introducing the classical expressions used to describe screened thermonuclear reactions in astrophysics and other applications, then discuss a quantum-mechanical approach based on time-dependent scattering theory. This QM approach corresponds to the classical equations in most cases, but gives significant deviations from the famous Salpeter screening factor at very low temperatures. Examples will be given for light TN reactions, along with some speculations about how screened carbon burning might be affected in cold dense astrophysical environments.