Restricted projections and Fourier decoupling in ${\mathbb{Q}}_p^n$

We prove a restricted projection theorem for Borel subsets of ${\mathbb{Q}}_p^n$ in the regime $p>n$. This generalizes results of Gan-Guo-Wang in the real setting. Our result is effective in the sense that explicit constants are obtained for various covering numbers. Along the way, we prove a fully explicit Fourier decoupling theorem for the moment curve in $p$-adic Cartesian space.