Black hole shadow and black hole thermodynamics

Abstract

We investigate the relations between the black hole shadow and black hole thermodynamics. We first show that phase structures of the black holes can be characterized by the shadow radii of the black holes. Then according to the second law of the black hole thermodynamics, we propose that the shadow radius of the black hole does not decrease with time. Lastly, the minimal sizes of the black hole shadows are given considering the third law of the black hole thermodynamics.