Thin accretion disks in f(R) modified gravity models

TL;DR

This paper investigates the properties of thin accretion disks around black holes in f(R) modified gravity, deriving solutions and emission spectra to identify potential observational signatures that distinguish these models from general relativity.

Contribution

It provides exact Schwarzschild-like solutions in f(R) gravity with additional terms and analyzes their impact on accretion disk emissions, offering a way to test modified gravity through astrophysical observations.

Findings

Exact solutions with linear and logarithmic corrections to Schwarzschild metric.

Differences in energy flux and emission spectra compared to general relativity.

Potential observational signatures to test f(R) gravity models.

Abstract

We consider the basic physical properties of matter forming a thin accretion disc in the static and spherically symmetric space-time metric of the vacuum $f(R)$ modified gravity models. The Lagrangian of the generalized gravity theory is also obtained in a parametric form, and the conditions of the viability of the model are discussed. The exact Schwarzschild type solution of the gravitational field equations in the $f(R)$ gravity contains a linearly increasing term, as well as a logarithmic correction, as compared to the standard Schwarzschild solution of general relativity, and it depends on four arbitrary integration constants. The energy flux and the emission spectrum from the accretion disk around the $f(R)$ gravity black holes are obtained, and they are compared to the general relativistic case. Particular signatures can appear in the electromagnetic spectrum, thus leading to the possibility of directly testing modified gravity models by using astrophysical observations of the emission spectra from accretion disks.