Reduced Kiselev black hole

TL;DR

This paper investigates the properties of a reduced Kiselev black hole, focusing on its causal structure, thermodynamics, shadow, and weak-field limit, especially in the less-studied parameter region where the fluid pressure is positive.

Contribution

It provides a detailed analysis of the reduced Kiselev black hole, a less-explored case with positive tangential pressure, including its causal structure, thermodynamics, and observational features.

Findings

Emergence of a new black hole horizon in the specified parameter region

Distinct thermodynamic behavior compared to traditional Kiselev black holes

Altered shadow and weak-field gravitational effects

Abstract

The Kiselev model describes a black hole surrounded by a fluid with equations of state $p_r/\rho=-1$ and $p_t/\rho=(3w+1)/2$ respectively in radial and tangential directions. It has been extensively studied in the parameter region $-1<w<-1/3$. If one rids off the black hole and turns to the region $-1/3<w<0$, i.e. $p_t>0$, then a new horizon of black hole type will emerge. This case has been mentioned in Kiselev's pioneer work but seldom investigated in the literature. Referring to it as reduced Kiselev black hole, we revisit this case with attention to its causal structure, thermodynamics, shadow cast and weak-field limit. An alternative interpretation and extensions of the black hole are also discussed.