Cosmological constant corrections to the photon sphere and black hole shadow radii

TL;DR

This paper reviews how the cosmological constant affects the photon sphere and black hole shadow radii, finding that these corrections are negligible for current observational targets like those of the Event Horizon Telescope.

Contribution

It provides a detailed calculation of cosmological constant corrections to black hole shadow radii for different dark energy models.

Findings

Corrections are very small for black holes observed by the Event Horizon Telescope.

Different dark energy models produce similar negligible effects on shadow sizes.

Abstract

We review the equations determining the photon sphere radius and the black hole shadow radius, and calculate the cosmological constant corrections arising when the dark energy action has the usual form, and when dark energy arises from a Weyl scaling invariant dark energy action. For black hole targets of the Event Horizon Telescope, the corrections are very small.