Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMotion and collision of particles near DST Black holes
78
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We consider Deser-Sarioglu-Tekin (DST) black holes as background and we study such the motion of massive particles as the collision of two spinning particles in the vicinity of its horizon. New kinds of orbits are allowed for small deviations of General Relativity, but the behavior of the collision is similar to the one observed for General Relativity. Some observables like bending of light and the perihelion precession are analyzed.
rate research
Read More
We compute the gravitational wave energy $E_{rm rad}$ radiated in head-on collisions of equal-mass, nonspinning black holes in up to $D=8$ dimensional asymptotically flat spacetimes for boost velocities $v$ up to about $90,%$ of the speed of light. We identify two main regimes: Weak radiation at velocities up to about $40,%$ of the speed of light, and exponential growth of $E_{rm rad}$ with $v$ at larger velocities. Extrapolation to the speed of light predicts a limit of $12.9,%$ $(10.1,~7.7,~5.5,~4.5),%$. of the total mass that is lost in gravitational waves in $D=4$ $(5,,6,,7,,8)$ spacetime dimensions. In agreement with perturbative calculations, we observe that the radiation is minimal for small but finite velocities, rather than for collisions starting from rest. Our computations support the identification of regimes with super Planckian curvature outside the black-hole horizons reported by Okawa, Nakao, and Shibata [Phys.~Rev.~D {bf 83} 121501(R) (2011)].
In this paper, we investigate a class of $5$-dimensional black holes in the presence of Gauss-Bonnet gravity with dyonic charges. At first step, thermodynamical quantities of the black holes and their behaviors are explored for different limits. Thermal stability and the possibility of the van der Waals like phase transition are addressed and the effects of different parameters on them are investigated. The second part is devoted to simulation of the trajectory of particles around these black holes and investigation of the angular frequency of particles motion. The main goal is understanding the effects of higher curvature gravity (Gauss-Bonnet gravity) and magnetic charge on the structure of black holes and the geodesic paths of particles moving around these black holes.
We describe a model that generates first order adiabatic EMRI waveforms for quasi-circular equatorial inspirals of compact objects into rapidly rotating (near-extremal) black holes. Using our model, we show that LISA could measure the spin parameter of near-extremal black holes (for $a gtrsim 0.9999$) with extraordinary precision, $sim$ 3-4 orders of magnitude better than for moderate spins, $a sim 0.9$. Such spin measurements would be one of the tightest measurements of an astrophysical parameter within a gravitational wave context. Our results are primarily based off a Fisher matrix analysis, but are verified using both frequentest and Bayesian techniques. We present analytical arguments that explain these high spin precision measurements. The high precision arises from the spin dependence of the radial inspiral evolution, which is dominated by geodesic properties of the secondary orbit, rather than radiation reaction. High precision measurements are only possible if we observe the exponential damping of the signal that is characteristic of the near-horizon regime of near-extremal inspirals. Our results demonstrate that, if such black holes exist, LISA would be able to successfully identify rapidly rotating black holes up to $a = 1-10^{-9}$ , far past the Thorne limit of $a = 0.998$.
We develop a new perturbation method to study the dynamics of massive tensor fields on extremal and near-extremal static black hole spacetimes in arbitrary dimensions. On such backgrounds, one can classify the components of massive tensor fields into the tensor, vector, and scalar-type components. For the tensor-type components, which arise only in higher dimensions, the massive tensor field equation reduces to a single master equation, whereas the vector and scalar-type components remain coupled. We consider the near-horizon expansion of both the geometry and the field variables with respect to the near-horizon scaling parameter. By doing so, we reduce, at each order of the expansion, the equations of motion for the vector and scalar-type components to a set of five mutually decoupled wave equations with source terms consisting only of the lower-order variables. Thus, together with the tensor-type master equation, we obtain the set of mutually decoupled equations at each order of the expansion that govern all dynamical degrees of freedom of the massive tensor field on the extremal and near-extremal static black hole background.
We discuss a new perturbation method to study the dynamics of massive vector fields on (near-)extremal static black hole spacetimes. We start with, as our background, a rather generic class of warped product metrics, and classify the field variables into the vector(axial)- and scalar(polar)-type components. On this generic background, we show that for the vector-type components, the Proca equation reduces to a single master equation, whereas the scalar-type components remain to be coupled. Then, focusing on the case of (near-)extremal static black holes in four-dimensions, we consider the near-horizon expansion of both the background geometry and massive vector field by a scaling parameter $lambda$ with the leading-order geometry being the so called near-horizon geometry. We show that on the near-horizon geometry, thanks to its enhanced symmetry, the Proca equation for the scalar-type components also reduces to a set of two mutually decoupled homogeneous wave equations for two variables, plus a coupled equation through which the remaining variable is determined. Therefore, together with the vector-type master equation, we obtain the set of three decoupled master wave equations, which govern the three independent dynamical degrees of freedom of the massive vector field in four-dimensions. We further expand the geometry and massive vector field with respect to $lambda$ and show that at each order, the Proca equation for the scalar-type components can reduce to a set of decoupled inhomogeneous wave equations whose source terms consist only of the lower-order variables, plus one coupled equation that determins the remaining variable. Therefore, if one solves the master equations on the leading-order near-horizon geometry, then in principle one can successively solve the Proca equation at any order.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
