Testing dynamical torsion effects on the charged black hole's shadow, deflection angle and greybody with M87* and Sgr A* from EHT

Abstract

Poincare Gauge's theory of gravity is the most noteworthy alternative extension of general relativity that has a correspondence between spin and spacetime geometry. In this paper, we used Reissner-Nordstrom-de Sitter and anti-de Sitter solutions, where torsion τ is added as an independent field, to analyze the weak deflection angles α of massive and null particles in finite distance regime. We then applied α to determine the Einstein ring formation in M87* and Sgr. A* and determine that relative to Earth's location from these black holes, massive torsion effects can provide considerable deviation, while the cosmological constant's effect remains negligible. Furthermore, we also explored how the torsion parameter affects the shadow radius perceived by both static and co-moving (with cosmic expansion) observers in a Universe dominated by dark energy, matter, and radiation. Our findings indicate that torsion and cosmological constant parameters affect the shadow radius differently between observers in static and co-moving states. We have also shown how the torsion parameter affects the luminosity of the photonsphere by studying the shadow with infalling accretion. The calculation of the quasinormal modes, greybody bounds, and high-energy absorption cross-section was also affected by the torsion parameter considerably.

Shadow, lensing, quasinormal modes, greybody bounds and neutrino propagation by dyonic ModMax black holes

“…Werner then improved this method for rotating spacetimes such as Kerr black hole [78]. Afterwards, this method was applied to various asymptotically flat spacetimes and was also extended to non-asymptotically flat spacetimes [39][40][41][42][43][44][45][46][47][48][79][80][81][82][83][84][85][86][87][88][89][90][91][92].…”

New black hole solutions with a dynamical traceless nonmetricity tensor in Metric-Affine Gravity

“…The aforementioned findings achieved by including the traceless part of the nonmetricity tensor into the geometrical framework open the door not only to further phenomenological analyses on this sector of the theory (see [56][57][58][59][60][61][62][63][64][65] for a recent list of observational constraints on extended theories of gravity), but also to new studies concerning the stability of the tensor modes displayed by the action (103). Indeed, whereas the stability of the scalar and vector modes of the torsion and nonmetricity tensors has been analysed in detail for quadratic MAG models [66][67][68][69][70], a thorough study concerning the behaviour of the tensor parts is yet to be performed.…”

Generalized Extended Uncertainty Principle Black Holes: Shadow and Lensing in the Macro- and Microscopic Realms

“…where b crit is a function of the photonsphere given in Equation (13). A spacetime may have a different expression for h(r), thus for a general spacetime, the critical impact parameter reads [61]:…”

“…with the critical impact parameter from Equation ( 16) [61], resulting to Equation (17). In choosing the value of b it is essential to note that the ratio, b/b crit , must not be significantly far from 1.…”