Nonlinear interaction between the electromagnetic fields (EMF) are occurred when vacuum polarization in quantum electrodynamics (QED) happens. The field of nonlinear electrodynamics which may be resulting from this interaction could have important effects on black hole physics. In this paper, we consider 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 Gauss-bonnet theorem in weak field limits, shadow cast using null geodesics method, and thin accretion disk using the Novikov-Thorne model, in particular, the time averaged energy flux, the disk temperature, the differential luminosity, the different emission profiles, and infalling spherical accretion are studied. Then we show how the physical quantities dependence 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.
We study the greybody factors, quasinormal modes, and shadow of the higher dimensional de-Sitter (dS)/anti de-Sitter (AdS) black hole spacetimes derived from the Einstein-bumblebee gravity theory within the Lorentz symmetry breaking (LSB) framework. We specifically apply the semi-analytical WKB method and the time domain approach to study the scalar and Dirac perturbations of the black hole. In-depth researches are done on the effects of the LSB and dimensionality on the bosonic/fermionic greybody factors, quasinormal modes, and shadow of the higher dimensional bumblebee black hole. The results obtained are discussed, tabulated, and illustrated graphically.
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 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 nonnegligible influences of modified gravity in astrophysical scenarios in high-density regimes but also reveals that the bounds on the fundamental parameters can be much stronger under alternate gravity theories.
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