Dynamical Property of Black Hole Matter
Matter loses its original characteristics after entering a black hole, thus becoming a new kind of (black hole) matter. The property of this new matter cannot be measured experimentally, but some of it can be deduced theoretically from the Einstein equations and the conservation laws which it must still satisfy. In a previous paper, this matter is modelled by an ideal fluid, with an equation of state $p(r)=-ξ\r(r)$ between the pressure $p(r)$ and the density $ρ(r)$. In order for this matter to fill the inside of a black hole so that its property can be teased out from the Einstein and conservation equations, it must possess a negative pressure ($ξ>0$) to counter the gravitation attraction which draws all matter to the center. In that case a solution of the Einstein and conservation equations exists if and only if the constant $ξ$ is confined within a narrow range, between 0.1429 and 0.1716. In the present paper, we try to find out its dynamical response by injecting additional matter into the black hole over a period of time. The resulting solutions of the six time-dependent Einstein equations and conservation laws are presented in perturbation theory, valid if the total amount of injection is small. Even in perturbation, the solutions can be obtained only with a special trick. The result shows that the equation of state $p(r,t)=-ξ\r(r,t)$ remains unchanged with the same $ξ$ when the injection rate is constant. When the rate changes with time, $ξ$ requires a correction, $ξ\toξ+ξ_1(r,t)$, where $ξ_1(r,t)$ appears to be correlated with the acceleration of the injected matter in a way to be shown in the text.