Small data scattering for a cubic Dirac equation with Hartree type nonlinearity in ${\mathbb{R}}^{1+3}$

We prove that the initial value problem for the Dirac equation $ \left ( -i\gamma^\mu \partial_\mu + m \right) \psi = \left(\frac{e^{- |x|}}{|x|} \ast ( \overline \psi \psi)\right) \psi \quad $\text{in }$ \ \R^{1+3} $ is globally well-posed and the solution scatters to free waves asymptotically as $t\to \pm \mathrm{\infty }$, if we start with initial data that is small in $H^s$ for $s>0$. This is an almost critical well-posedness result in the sense that $L^2$ is the critical space for the equation. The main ingredients in the proof are Strichartz estimates, space-time bilinear null-form estimates for free waves in $L^2$, and an application of the $U^p$ and $V^p$-function spaces.