Kerr-Anti-De-Sitter/De-Sitter Black Hole In Perfect Fluid Dark Matter Background


الملخص بالإنكليزية

We obtain the Kerr-anti-de-sitter (Kerr-AdS) and Kerr-de-sitter (Kerr-dS) black hole (BH) solutions to the Einstein field equation in the perfect fluid dark matter background using the Newman-Janis method and Mathematica package. We discuss in detail the black hole properties and obtain the following main results: (i) From the horizon equation $g_{rr}=0$, we derive the relation between the perfect fluid dark matter parameter $alpha$ and the cosmological constant $Lambda$ when the cosmological horizon $r_{Lambda}$ exists. For $Lambda=0$, we find that $alpha$ is in the range $0<alpha<2M$ for $alpha>0$ and $-7.18M<alpha<0$ for $alpha<0$. For positive cosmological constant $Lambda$ (Kerr-AdS BH), $alpha_{max}$ decreases if $alpha>0$, and $alpha_{min}$ increases if $alpha<0$. For negative cosmological constant $-Lambda$ (Kerr-dS BH), $alpha_{max}$ increases if $alpha>0$ and $alpha_{min}$ decreases if $alpha<0$; (ii) An ergosphere exists between the event horizon and the outer static limit surface. The size of the ergosphere evolves oppositely for $alpha>0$ and $alpha<0$, while decreasing with the increasing $midalphamid$. When there is sufficient dark matter around the black hole, the black hole spacetime changes remarkably; (iii) The singularity of these black holes is the same as that of rotational black holes. In addition, we study the geodesic motion using the Hamilton-Jacobi formalism and find that when $alpha$ is in the above ranges for $Lambda=0$, stable orbits exist. Furthermore, the rotational velocity of the black hole in the equatorial plane has different behaviour for different $alpha$ and the black hole spin $a$. It is asymptotically flat and independent of $alpha$ if $alpha>0$ while is asymptotically flat only when $alpha$ is close to zero if $alpha<0$.

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