A new asymptotical flat and spherically symmetric solution in the generalized Einstein-Cartan-Kibble-Sciama gravity and gravitational lensing

TL;DR

This paper introduces a new spherically symmetric solution in generalized Einstein-Cartan-Kibble-Sciama gravity, analyzing photon propagation and gravitational lensing, revealing unique features like finite deflection angles near horizons in certain cases.

Contribution

It presents a novel asymptotically flat, spherically symmetric solution in ECKS gravity and explores its implications for photon trajectories and gravitational lensing effects.

Findings

Existence of a special case with horizon but no photon sphere.

Finite deflection angle near the horizon in this special case.

Parameters significantly influence strong gravitational lensing coefficients.

Abstract

We firstly present a new asymptotical flat and spherically symmetric solution in the generalized Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity and then investigate the propagation of photon in this background. This solution possesses three independent parameters which affect sharply photon sphere, deflection angle of light ray and gravitational lensing. Since the condition of existence of horizons is not inconsistent with that of photon sphere, there exists a special case where there is horizon but no photon sphere in this spacetime. Especially, we find that in this special case, the deflection angle of a light ray near the event horizon tends to a finite value rather than diverges, which is not explored in other spacetimes. We also study the strong gravitational lensing in this spacetime with the photon sphere and then probe how the spacetime parameters affect the coefficients in the strong field limit.