Asymptotics of the radiation field for the massless Dirac-Coulomb system

Abstract

We consider the long-time behavior of the massless Dirac equation coupled to a Coulomb potential. For nice enough initial data, we find a joint asymptotic expansion for solutions near the null and future infinities and characterize explicitly the decay rates seen in the expansion. This paper can be viewed as a successor to previous work on asymptotic expansions for the radiation field. The key new elements are propagation estimates near the singularity of the potential, building on work of the first author with Wunsch and an explicit calculation with hypergeometric functions to determine the rates of decay.