# Effect of null aether field on weak deflection angle of black holes

## TL;DR

This paper investigates how null aether theory influences the weak gravitational lensing effect of black holes by calculating the deflection angle using the Gauss-Bonnet theorem, revealing the topological nature of light bending.

## Contribution

It introduces a novel analysis of light deflection in null aether theory using the Gauss-Bonnet theorem, highlighting the topological aspects of gravitational lensing in this context.

## Key findings

- Null aether field modifies the weak deflection angle of black holes.
- Gravitational lensing is shown to be a global, topological effect.
- The Gauss-Bonnet theorem effectively computes light bending in NAT.

## Abstract

We study the light rays in a static and spherically symmetric gravitational field of null aether theory (NAT). To this end, we employ the Gauss-Bonnet theorem to compute the deflection angle by a NAT black hole in the weak limit approximation. Using the optical metrics of the NAT black hole, we first obtain the Gaussian curvature and then calculate the leading terms of the deflection angle. Our calculations show how gravitational lensing is affected by the NAT field. We also show once again that the bending of light stems from a global and topological effect.