Center for Theoretical Physics of the Universe (CTPU-PTC)

Shadow formation in gravitational collapse and effect of redshift by spacetime dynamics

by Yasutaka Koga (Nagoya University)

Seminar Room (CTPU)

Seminar Room


Black hole shadow observation is a key observation for testing gravity and geometry in the vicinity of a black hole. An ideal but interesting case is shadow of a black hole which is formed by gravitational collapse of a transmissive compact object. In the case, shadow is formed as a consequence of redshift of lights and the redshift is essentially caused by the spacetime dynamics. In this talk, we especially focus on the relation between redshift of lights and spacetime dynamics.
First, we investigate a collapsing spherical shell model and study the redshift of lights due to the dynamics. We see that actually the dynamics of gravitational collapse causes redshift of most of lights. Second, we consider gravitational collapse of a general spherically symmetric object and propose a covariant formula that gives redshift of lights in terms of curvature tensor. With the formula, we discuss how the redshift of lights can be understood in gravitational collapse.