AdS Black Hole with Phantom Scalar Field

Figure 1

The black hole temperature in terms of entropy. The dashed green line represents the Hawking-Page transition temperature, while the solid red line stands for . When , there is only a thermal gas solution in the AdS space. When , for a given temperature , there exist two black hole solutions given by (23). The one with large horizon is stable, while it is thermodynamically unstable for the smaller one.