Small data scattering of 2d Hartree type Dirac equations

In this paper, we study the Cauchy problem of 2d Dirac equation with Hartree type nonlinearity $c(|\cdot|^{-\gamma} * \langle \psi, \beta \psi\rangle)\beta\psi$ with $c\in \mathbb R\setminus\{0\}$, $0 < \gamma < 2$. Our aim is to show the small data global well-posedness and scattering in $H^s$ for $s > \gamma-1$ and $1 < \gamma < 2$. The difficulty stems from the singularity of the low-frequency part $|\xi|^{-(2-\gamma)}\chi_{\{|\xi|\le 1\}}$ of potential. To overcome it we adapt $U^p-V^p$ space argument and bilinear estimates of \cite{yang, tes2d} arising from the null structure. We also provide nonexistence result for scattering in the long-range case $0 < \gamma \le 1$.