Constant-drift massive elliptic estimate
= Constant-drift massive elliptic estimate
For real $m\ne0$ and constant real $\alpha$, the Fourier symbol of $-\Delta-\alpha\cdot\nabla+m^2$ has modulus at least $|\xi|^2+m^2$. Its inverse therefore maps $L^2$ into $H^2$ with norm at most $\max(1,m^{-2})$, uniformly in the drift.