Dynamics of accretion disks in a constant curvature f ( R ) $f(R)$ -gravity

Abstract

So far 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 (Pun et al. in Phys. Rev. D 78:024043, 2008) and building radiative models of thin accretion disks for both Schwarzschild and Kerr black holes in f (R) gravity (Perez et al. in Astron. Astrophys. 551:4, 2013) were addressed properly. Also von Zeipel surfaces and convective instabilities in f (R)-Schwarzschild(Kerr) background have been investigated recently (Alipour et al. in Mon. Not. R. Astron. Soc. 454:1992Soc. 454: , 2015. In this streamline, here we study the effects of radial and angular pressure gradients on thick accretion disks in Schwarzschild geometries in a constant curvature f (R) modified gravity. Since thick accretion disks have high accretion rate, we study configuration and structure of thick disks by focusing on the effect of pressure gradient on formation of the disks. We clarify our study by assuming two types of equation of state: polytropic and Clapeyron equation of states.

Astrophysical Constraints on Strong Modified Gravity

“…Ahmed and coworkers 117,118 analyzed some aspects of the Michel-type accretion onto static spherically symmetric black holes in f (R)-gravity. Effects of radial and angular pressure gradients on thick accretion disks in f (R)-Schwarzschild geometry with constant Ricci curvature were investigated by Alipour et al 119 Bhattacharjee and collaborators 120 researched additional sources of vorticity in accreted material by black holes, others than the classical baroclinic instability. In particular, they analyzed how the spacetime geometry contributes to the vorticity generation in accretion disk plasma, both in GR and f (R)-gravity with constant Ricci scalar.…”

Magnetized discs and photon rings around Yukawa-like black holes

“…The two solutions are compared with the aim of exploring whether the extended f (R) theory involving a Yukawa-like potential can still be valid with current observations. Previous attempts to construct accretion discs around black holes in f (R) theories of gravity can be found in Pérez et al [59] and Alipour et al [60] for thin and thick discs, respectively.…”