arXiv subjects

Akhil Uniyal

Publications and source records attributed to Akhil Uniyal.

21 records · Page 2Linked to original sources

arXiv2023

Constraining fundamental parameters in modified gravity using Gaia-DR2 massive white dwarf observation

Various experiments and observations have led researchers to suggest different bounds on fundamental constants like the fine-structure constant and the proton-to-electron mass ratio. These bounds differ mostly due to the energy scale of the systems where the experiments are performed. In this article, we obtain bounds on these parameters in the modified gravity context using the Gaia-DR2 massive white dwarf data and show that the bounds alter as the gravity theory changes. This exploration not only indicates strong support for non-negligible influences of modified gravity in astrophysical scenarios in high-density regimes but also reveals that the bounds on fundamental parameters can be much stronger under alternate gravity theories.

gr-qc↗

arXiv2023

Nonlinearly charged black holes: Shadow and Thin-accretion disk

In this paper, we explore the effect of non-linear electrodynamics (NLED) parameters and magnetic charges on various aspects of black holes, like how they bend light, how they emit radiation, and how they appear as a shadow by considering a thin accretion disk model. We initially examine the overall behavior of the photonsphere and the corresponding shadow silhouette under the effects of these parameters. Using the EHT data for Sgr. A* and M87*, we aim to find constraints for $q_m$. Our results indicate that M87* gives better constraints, and as the value of $β$ is varied to increase, the constrained range for $q_m$ widens. At lower values of $q_m$, we find that the shadow radius is close to the observed value. Then, we study different things like how much energy the black hole emits, the temperature of the disk around it, and the kind of light it gives off. We also look at how the black hole shadow appears in different situations. We also study how matter falls onto the black hole from all directions. Finally, we investigate how the magnetic charge affects all these things when we take into account a theory called NLED along with gravity. This study helps us understand the complex relationship between magnetic charge and black holes.

gr-qc↗

arXiv2023

Probing a nonlinear electrodynamics black hole with thin accretion disk, shadow and deflection angle with M87* and Sgr A* from EHT

Non-linear interaction between the electromagnetic fields (EMF) occurs when vacuum polarization in quantum electrodynamics (QED) happens. The field of non-linear electrodynamics, which may result from this interaction, could have important effects on black hole physics. This paper considers the asymptotically flat black hole solution in Einstein-nonlinear electrodynamics (NLE) fields. We study the effect of the NLE parameters on the black hole deflection angle using the Gauss-Bonnet theorem in weak field limits, shadow cast using the null geodesics method, and thin accretion disk using the Novikov-Thorne model. In particular, we studied the time-averaged energy flux, the disk temperature, the differential luminosity, the different emission profiles, and infalling spherical accretion. Then we show how the physical quantities depend on $β$ and $C$ parameters of NLE and provide some constraints on the NLE parameters using the observations of M87* and Sgr A* from EHT.

gr-qc↗