We determine the largest non-trivial rate of exponential decay at infinity for solutions to the Dirac equation \begin{ equation*} \mathcal{ D}_n \psi + \mathbb{ V} \psi = 0 \quad \text{ in }\mathbb{ R}^n, \end{ equation*} being $\mathcal{ D}_n$ the massless Dirac operator in dimension $n\geq 2$ and $\mathbb{ V}$ a (possibly non-Hermitian) matrix-valued perturbation such that $|\mathbb{ V}(x)| \sim |x|^{ -\epsilon}$ at infinity, for $-\infty < \epsilon < 1$. Moreover, we show that our results are sharp for $n =2,3$, providing explicit examples of solutions that have the prescripted decay, in presence of a potential with the related behaviour at infinity.
Categories: math.AP