Approach to a Cauchy Problem in Stability Study of the Schwarzschild Black Hole

Generally, the Schwarzschild black hole is proven to be stable by two different methods: the mode-decomposition method and the integral method. We show that the integral method can only apply to the initial data vanishing at both the horizon and the spatial infinity. It can not treat the initial data only vanishing at the spatial infinity. We give an example to show the misleading information caused by the use of tortoise coordinates in the perturbation equations. Subsequently, the perturbation equations in the Schwarzschild coordinates are shown to be insufficient for the stability study.