We study the coupling of massive scalar fields to matter in orbit around rotating black holes. It is generally expected that orbiting bodies will lose energy gravitational waves, slowly inspiraling into hole. Instead, we show field leads a surprising effect: because superradiance, can hover "floating orbits" for which net loss at infinity entirely provided by hole's rotational energy. Orbiting remain floating until they extract sufficient angular momentum from hole, or perturbations...

We consider a universal relation between moment of inertia and quadrupole arbitrarily fast rotating neutron stars. Recent studies suggest that this breaks down for rotation. find it is still among various suggested equations state constant values certain dimensionless parameters characterizing the magnitude One these includes star radius, leading to new expressing radius through mass, frequency, spin parameter. This can become powerful tool measurements.

In this work, we study the behavior of null geodesics within a rotating Teo wormhole spacetime in nonmagnetized pressureless plasma. The wormholes are an explicit class that generalizes static, spherically symmetric ones, initially considered by Morris and Thorne. By focusing on dispersion relation plasma disregarding its direct gravitational effects, examine how light rays traverse abovementioned spacetime. A key highlight work is necessity specific distribution profile to establish...

Previous works on black hole shadows have been primarily focused studying in asymptotically flat and anti--de Sitter space times. In the present work, we find general expressions for de shadow as seen by static comoving observers, any spherically symmetric solution, time dimension generic theories of gravity. As test cases, use derived to study three different solutions: four dimensional Reissner-Nordstr\"om hole, recently proposed Gauss Bonnet five hole.

Abstract We find the low lying quasinormal mode frequencies of recently proposed novel four dimensional Gauss–Bonnet de Sitter black holes for scalar, electromagnetic and Dirac field perturbations using third order WKB approximation as well Padé approximation, an improvement over WKB. figure out effect coupling $$\alpha $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi></mml:math> cosmological constant $$\Lambda...

Abstract We investigate the relativistic, viscous, advective neutrino-dominated accretion flows (NDAFs) around rotating stellar-mass black holes, incorporating neutrino cooling. By adopting an effective potential to describe spacetime geometry we self-consistently solve governing NDAF equations obtain global transonic solutions. Our findings indicate that, depending on model parameters, namely, energy ( ε ), angular momentum λ rate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...

We apply an effective field theory method for the gravitational interaction of compact stars, developed within context general relativity, to Newtonian gravity. In this theory, a object is represented by point particle possessing generic multipole moments. The time evolution multipoles depends on excitations due external fields. This can formally be described response function applied poles correspond normal oscillation modes star. gives rise resonances between and tidal forces in binary...

We study the relativistic accretion flow in a generic stationary axisymmetric space-time and obtain an effective potential (${\mathrm{\ensuremath{\Phi}}}^{\mathrm{eff}}$) that accurately mimics general features of Kerr black hole having spin $0\ensuremath{\le}{a}_{\mathrm{k}}<1$. Considering disc to be confined around equatorial plane rotating using equation state, we examine properties compare them with same obtained form semirelativistic as well nonrelativistic flows. Towards this, first...

It is well known that Ultra-Light Dark Matter (ULDM), usually scalar fields of mass $m \sim 10^{-22}~{\rm eV}$, can solve some the outstanding problems Cold (CDM) paradigm. Such a field could have non-negligible self-coupling $\lambda$. In this work, using observational upper limit on amount centrally concentrated dark matter in galaxy, we arrive at constraints $\lambda - m$ (self coupling $-$ mass) parameter space. found $m$ ULDM depends upon sign and strength self-interactions. We...

We elaborate on a powerful tidal interaction formalism where the multipole dynamics is kept generic and encoded in linear response function. This function gravitational counterpart of atomic spectrum can become similar importance with rise wave astronomy. find that internal nonrotating neutron stars admit harmonic oscillator formulation yielding simple interpretation tides. A preliminary investigation black holes case given. Our results fill gap between Love numbers dynamic

So far the study of black hole perturbations has been mostly focussed upon classical holes with singularities at origin and hidden by event horizon. Compared to that, regular are a completely new class solutions arising out modification general theory relativity coupling gravity an external form matter. Therefore it is extremely important behaviour such under different types perturbations. Recently Bardeen solution de Sitter branch proposed Fernando. We compute quasi-normal (QN) frequencies...

We study the stability of an asymptotically flat, static, spherically symmetric naked singularity spacetime in novel four-dimensional Einstein-Gauss-Bonnet (EGB) gravity. The EGB black hole for large enough values coupling parameter leads to such a singularity. and response are studied against perturbations by test scalar, electromagnetic Dirac fields, time evolution these was observed numerically. Implementing null Dirichlet boundary condition near singularity, we that $l=1$ modes...

Holographic properties of a finite density fermion system have been shown to exhibit many interesting behaviours which can be observed in future. In this paper, we study low energy the framework holographic Mott-Insulator system. We nature Fermi surface and its evolution by tuning two types dipole couplings bulk. further introduce translational symmetry breaking complex scalar field, is assumed couple with fermions. The background induced field known as Q-lattice. calculate spectral...

Bardeen de-Sitter (BdS) black hole is a spherically symmetric solution of Einstein's equation which coupled to nonlinear electromagnetic field in way that one gets regular solution, devoid any singularity at the origin. We compute quasinormal (QN) frequencies for BdS due and gravitational perturbations. analyse behaviour both real imaginary parts QN by varying parameters compare with Reissner-Nordström (RN-dS) hole. Interestingly, we find response RN-dS holes under perturbations are...

We have investigated the characteristics of shadows cast by Kerr black hole in presence plasma and compared them to those a rotating wormhole uniform space-time for an observer at infinity. Interestingly, same density, apparent shadow size is always greater than that hole. To further distinguish two compact objects we studied deflection angle did comparative study non-uniform profiles. The goal this whole exercise deepen our understanding observational phenomena these astrophysical objects....

In this paper, we analyze the pole-skipping phenomena of finite temperature Yang-Mills theory with quark flavors, which is dual to D3-D7 brane systems in bulk. We also consider external electric field boundary theory, world volume on D7 brane. will work probe limit where branes do not backreact D3 background. scenario, decode characteristic parameters chaos, namely, Lyapunov exponent <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...

We obtain an analytic expression for the highly damped asymptotic quasinormal mode frequencies of (d ≥ 5)-dimensional Schwarzschild black hole modified by Gauss–Bonnet term, which appears in string derived models gravity. The is obtained under inspired assumption that there exists a minimum length scale system and limit when coupling front term action small. Although are several similarities this geometry with hole, quite different. In particular, real part class single horizon holes not...