Light trajectories and optical appearances in asymptotically Anti-de Sitter-Schwarzschild and black string space-times

TL;DR

This paper investigates how light trajectories and optical images differ in asymptotically Anti-de Sitter space-times, specifically for Schwarzschild-AdS black holes and black strings, to aid future observational tests of alternative black hole models.

Contribution

It introduces the analysis of light trajectories and images in asymptotically AdS space-times, extending previous flat-space studies to new geometries relevant for testing gravitational theories.

Findings

Light trajectories are significantly affected by the AdS boundary conditions.

Images of black holes in AdS space differ from those in flat space.

Distinct features of black strings compared to Schwarzschild-AdS black holes.

Abstract

The Event Horizon Telescope (EHT) imaging of the central objects in the M87 and Milky Way galaxies provide compelling evidence that these objects are consistent with (Kerr) black holes. In view of these observations and the future expectations of Very Long Baseline Interferometry (VLBI) on which the EHT observations are based, an intensive research work has been carried out in the literature to simulating light trajectories and reconstructing the corresponding optical appearance for a wide array of modified black holes and ultra-compact objects. The corresponding images are directly affected not only by the background space-time geometry but also by the physics of the accretion disk, whose combination yields a characteristic fingerprint. In this paper, we consider such a fingerprint for objects which are not asymptotically flat but instead approach a Anti-de Sitter space-time. This assumption significantly influences light trajectories and, consequently, the corresponding images of the objects as seen by an observer at some distance, which can be used in future VLBI observations for testing alternatives of this kind to the Kerr paradigm. We illustrate our considerations with the examples of a Schwarzschild-Anti-de Sitter black hole and a black string, discussing their most notable departures from canonical, asymptotically-flat black hole space-times.