Gravitational lensing in modified gravity: a case study for Fast Radio Bursts

Over the last few decades, a plethora of modifications to general relativity have been proposed to solve a host of cosmological and astrophysical problems. Many modified gravity models are now ruled out with further astrophysical observations; some theories are still viable, with, at best, bounds on their parameters set by observations to date. More recently, observations of Fast Radio Bursts have proven to be remarkably powerful tools to constrain cosmology and fundamental physics. In this work, we consider a generic modified gravity theory and consider the implications for gravitational lensing with Fast Radio Bursts. We use a set of Fast Radio Burst observations to constrain the fraction of dark matter made up of primordial black holes in such a theory. We further show that modified gravity adds a screening effect on gravitational lensing similar to the case when there is plasma in the path of the light ray acting as a scattering screen.

Automated summary

In recent decades, numerous modifications to general relativity have been proposed to address cosmological and astrophysical issues. While many modified gravity models have been ruled out, some theories remain viable albeit with parameters constrained by observations. Fast Radio Bursts have proven to be powerful tools for constraining cosmology and fundamental physics. This study examines the implications of a generic modified gravity theory on gravitational lensing using Fast Radio Bursts, and utilizes observations to constrain the fraction of dark matter composed of primordial black holes. Additionally, it demonstrates that modified gravity produces a screening effect on gravitational lensing akin to the presence of plasma acting as a scattering screen.