We calculate the scalar-gravitational quasi-normal modes of equal angular momenta Myers-Perry black holes in odd dimensions. We find a new bar-mode (non-axisymmetric) classical instability for $D \ge 7$. These black holes were previously found to be unstable to axisymmetric perturbations for spins very near extremality. The bar-mode instability we find sets in at much slower spins, and is therefore the dominant instability of these black holes. This instability has important consequences for the phase diagram of black holes in higher dimensions.
The shadow of a black hole can be one of the strong observational evidences for stationary black holes. If we see shadows at the center of galaxies, we would say whether the observed compact objects are black holes. In this paper, we consider a formula for the contour of a shadow in an asymptotically-flat, stationary, and axisymmetric black hole spacetime. We show that the formula is useful for obtaining the contour of the shadow of several black holes such as the Kerr-Newman black hole and rotating regular black holes. Using the formula, we can obtain new examples of the contour of the shadow…
It is well known that all rotating perfect fluid stars in general relativity are unstable to certain non-axisymmetric perturbations via the Chandrasekhar-Friedman-Schutz (CFS) instability. However, the mechanism of the CFS instability requires, in an essential way, the loss of angular momentum by gravitational radiation and, in many instances, it acts on too long a timescale to be physically/astrophysically relevant. It is therefore of interest to examine the stability of rotating, relativistic stars to axisymmetric perturbations, where the CFS instability does not occur. In this paper, we pro…
Precession is one of the important mechanisms of gravitational wave generation in astrophysics. In general, free precession of a rigid body can be caused by the rotation of a triaxial body. In the case of symmetric body, if only the principal axis does not coincide with the axis of rotation, then there is the precession. When a symmetric body rotates around one of its principal axes, the body cannot move with precession. However, when there is a perturbation in angular velocity of the symmetric body spinning around the principal axis of the largest moment, the body can have a precession motion…
We describe a set of time evolution equations and its numerical implementation for the investigation of non-axisymmetric oscillations of rapidly rotating compact objects in full General Relativity, taking into account the contribution of a dynamic spacetime. We derive the perturbation equations for the spacetime in the Hilbert gauge, while the hydrodynamical evolution is based on perturbations of the energy-momentum tensor. In our numerical implementation, we use Kreiss-Oliger dissipation in order to achieve a stable time evolution. Our code features high accuracy at comparably low computation…
Stationary axisymmetric systems that allow for a separability structure
School of Liberal Arts and Sciences, Korea National University of Transportation(韩国交通大学生命科学与艺术学院);Center for Quantum Spacetime, Sogang University(西江大学量子时空中心)
Quasi-equilibrium models of uniformly rotating axisymmetric and triaxial quark stars are computed in general relativistic gravity scenario. The Isenberg-Wilson-Mathews (IWM) formulation is employed and the Compact Object CALculator (COCAL) code is extended to treat rotating stars with finite surface density and new equations of state (EOSs). Besides the MIT bag model for quark matter which is composed of de-confined quarks, we examine a new EOS proposed by Lai and Xu that is based on quark clustering and results in a stiff EOS that can support masses up to $3.3M_\odot$ in the case we considere…
Using the analogy between acoustic perturbations in an ideal fluid and the description of a Klein-Gordon scalar field in a curved spacetime, we study the quasinormal modes of a quantum system: the rotating Bose-Einstein condensate. To compute quasinormal frequencies, we use two different numerical techniques, namely the direct integration and the continued-fraction methods. We study in detail the ergoregion instability of this linearly perturbed system, comparing the results with different setup configurations.
Numerical simulations of oscillating and differentially rotating neutron stars
Université de Strasbourg(斯特拉斯堡大学);CNRS(法国国家科学研究中心);Observatoire astronomique de Strasbourg(斯特拉斯堡天文台);Sorbonne Université(索邦大学);Observatoire de Paris(巴黎天文台);PSL(巴黎文理研究大学);LUX, CNRS UMR 8262(LUX,法国国家科学研究中心联合研究实验室8262)
Gravitational waves from core collapse of rotating very-massive stars: 3D numerical relativity computation
The Pennsylvania State University(宾夕法尼亚州立大学);Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut)(马克斯·普朗克引力物理学研究所(阿尔伯特·爱因斯坦研究所));Kyoto University(京都大学);Tohoku University(东北大学)
Stationary axisymmetric metric describing the exterior field of a rotating, charged sphere endowed with magnetic dipole moment is presented and discussed. It has a remarkably simple multipole structure defined by only four nonzero Hoenselaers-Perjés relativistic moments.
In the literature, the Newman-Janis algorithm (NJA) has been widely used to construct stationary and axisymmetric spacetimes to describe rotating black holes. In addition, it has been recently shown that the general stationary and axisymmetric spacetime generated through NJA allows the complete separability of the null geodesic equations. In fact, the Hamilton-Jacobi equation in this spacetime is also separable if one of the metric functions is additively separable. In this work, we further study the conditions for a separable Klein-Gordon equation in such a general spacetime. The relations be…