Massless Majorana spinors in the Kerr spacetime

Abstract

In this paper, we show that massive Majorana spinors \eqref{1.2} do not exist if they are $t$-dependent or $\phi$-dependent in Kerr, or Kerr-(A)dS spacetimes. For massless Majorana spinors in the non-extreme Kerr spacetime, the Dirac equation can be separated into radial and angular equations, parameterized by two complex constants $\epsilon_1$, $\epsilon_2$. If at least one of $\epsilon_1$, $\epsilon_2$ is zero, massless Majorana spinors can be solved explicitly. If $\epsilon_1$, $\epsilon_2$ are nonzero, we prove the nonexistence of massless time-periodic Majorana spinors in the non-extreme Kerr spacetime which are $L^p$ outside the event horizon for $ 0<p\le\frac{6}{|\epsilon_1|+|\epsilon_2| +2}$. We then provide the Hamiltonian formulation for massless Majorana spinors and prove that the self-adjointness of the Hamiltonian leads to the angular momentum $a=0$ and spacetime reduces to the Schwarzschild spacetime, moreover, the massless Majorana spinor must be $\phi$-independent. Finally, we show that, in the Schwarzschild spacetime, for initial data with $L^2$ decay at infinity, the probability of the massless Majorana spinors to be in any compact region of space tends to zero as time tends to infinity.