相关论文: String effect on the relative time delay in the Ke…
It has been argued recently that string theory effects qualitatively modify the effective black hole geometry experienced by modes with radial momentum of order $1/\sqrt{\alpha'}$. At tree level, these $\alpha'$-effects can be explicitly…
Einstein-Maxwell dilaton-axion gravity is a string-inspired model arising from the low energy effective action of heterotic string theory and an important candidate as alternative to General Relativity. Recently, some authors have explored…
We study the geodesic equation in the space-time of a Kerr black hole pierced by an infinitely thin cosmic string and give the complete set of analytical solutions of this equation for massive and massless particles in terms of Mino time…
Einstein-Maxwell dilaton-axion (EMDA) gravity provides a simple framework to investigate the signatures of string theory. The axion and the dilaton fields arising in EMDA gravity have important implications in inflationary cosmology and in…
This dissertation aims at studying the braneworld models in the context proposed by Randall and Sundrum. The focus is on the spin-0 perturbations in the Kerr space-time as a 4-dimensional braneworld. The work deals the main aspects of…
We review recent results on near-horizon static black hole solutions and entropy in R^2-corrected N=2 SUGRA in D=5, focusing on actions connected to heterotic string compactified on K3\times S^1. Comparison with \alpha'-perturbative…
This work addresses spherically symmetric, static black holes in higher-derivative stringy gravity. We focus on the curvature-squared correction to the Einstein-Hilbert action, present in both heterotic and bosonic string theory. The string…
It is observed that the three-dimensional BTZ black hole is a supersymmetric solution of the low-energy field equations of heterotic string theory compactified on an Einstein space. The solution involves a non-zero dilaton and NS-NS…
Astrophysical phenomena involving massive black holes (BHs) in close binaries are expected to leave detectable signatures in the electromagnetic and gravitational-wave spectrum. Such imprints may provide precious information to probe the…
We studied the relativistic images caused by strong gravitational lensing in Kerr black hole images, which carry some essential signatures about the black hole space-time. We defined a new celestial coordinates whose origin is the center of…
In arXiv:1705.10172 it was proposed that string theory replaces Schwarzschild black holes with horizonless thin shells with an AdS interior. In this paper we extend the analysis to slowly rotating black holes, solving the Israel-Lanczos-Sen…
With an intent to explore the interplay between the Lorentz symmetry breaking (LSB) and the presence of dark matter (DM), we obtain a static and spherically symmetric black hole (BH) solution in the background of nonminimally coupled…
The target-space interpretation of the exact (in $\alpha'$) reflection coefficient for scattering from Euclidean black-hole horizons in classical string theory is studied. For concreteness, we focus on the solvable $SL(2,…
A black hole solution to three dimensional general relativity with a negative cosmological constant has recently been found. We show that a slight modification of this solution yields an exact solution to string theory. This black hole is…
We investigate the frame-dragging effect of the hairy Kerr spacetimes on the spin of a test gyro and accretion disk. Firstly, we analyze Lense-Thirring (LT) precession frequency, geodetic precession frequency, and the general spin…
String inspired models can serve as potential candidates to replace GR in the high energy regime where quantum gravity is expected to play a vital role. Such models not only subsume the ultraviolet nature of gravity but also exhibit…
We review recent developments in understanding quantum/string corrections to BPS black holes and strings in five-dimensional supergravity. These objects are solutions to the effective action obtained from M-theory compactified on a…
We study the BTZ black holes (2+1 dimensional space-time) in the low energy heterotic string theory (BTZ-Sen BH). This concept requires us to include a non-trivial dilaton $ \phi $ and a 3-form $ H_{\mu\nu\rho} $ field. By using the…
We study null rays propagation in a spacetime of static Schwarzschild--Tangherlini black holes in arbitrary number of dimensions. We focus on the bending angle and the retarded time delay for rays emitted in the vicinity of a black hole and…
We study the time delay between two relativistic images due to strong gravitational lensing of the light rays caused by the Kerr and Kerr-Newman black holes. The trajectories of the light rays are restricted on the equatorial plane. Using…