Black hole shadow and Wandering null geodesics

TL;DR

This paper investigates wandering null geodesics in black hole spacetimes, introducing the concept of 'black room' to better understand black hole shadows and their optical observations.

Contribution

It introduces the concept of 'black room' and analyzes wandering null geodesics, providing new insights into black hole shadows and optical phenomena.

Findings

Wandering null geodesics commonly exist in black hole spacetimes.

The 'black room' concept relates wandering geodesics to black hole shadows.

Continuity of geodesic solutions explains optical observations of event horizons.

Abstract

The role of the wandering null geodesic is studied in a black hole spacetime. Based on the continuity of the solution of the geodesic equation, the wandering null geodesics commonly exist and explain the typical phenomena of the optical observation of event horizons. Moreover, a new concept of `black room' is investigated to relate the wandering null geodesic to the black hole shadow more closely.