We consider Kerr-de Sitter spacetimes and evaluate their mass, angular momentum and entropy according to the boundary counterterm prescription. We provide a physicall interpretation for angular velocity and angular momentum at future/past infinity. We show that the entropy of the four-dimensional Kerr-de Sitter spacetimes is less than of pure de Sitter spacetime in agreement to the entropic N-b...

The remarkable and unexpected separability of the Hamilton-Jacobi and Klein-Gordon equations in the background of a rotating four-dimensional black hole played an important rôle in the construction of generalisations of the Kerr metric, and in the uncovering of hidden symmetries associated with the existence of Killing tensors. In this paper, we show that the Hamilton-Jacobi and Klein-Gordon eq...

Spherically symmetric static fluid sources are endowed with rotation and embedded in Kerr empty space-time up to an including quadratic terms in an angular velocity parameter using Darmois junction conditions. Einstein's equation's for the system are developed in terms of linear ordinary differential equations. The boundary of the rotating source is expressed explicitly in terms of sinusoidal f...

We present Kerr-AdS black holes with equal angular momenta in arbitrary odd spacetime dimensions ≥ 5. The solutions include three non-trivial parameters, mass, angular momentum and an additional parameter δ. For a special value of δ, by twisting the Killing vector fields of the black holes, we reproduce the compact Sasaki-Einstein manifolds constructed by Gauntlett, Martelli, Sparks and Waldram...

The magnetorotational instability(MRI) in the Kerr spacetime is studied on a 3+1 viewpoint. The Maxwell's equations are expressed in a circularly orbiting observer's frame that co-rotates with matter in Keplerian orbits. The hydromag-netic equations are represented in a locally nonrotating frame(LNRF). There exist large proper growth rates in MRI around a rapidly rotating black hole. The large ...

We demonstrate that the rotating black holes in an arbitrary number of dimensions and without any restrictions on their rotation parameters possess the same hidden symmetry as the four-dimensional Kerr metric. Namely, besides the spacetime symmetries generated by the Killing vectors they also admit the (antisymmetric) Killing-Yano and symmetric Killing tensors.

In Tb/Co multilayers, the saturation magnetization M, and the anisotropy constant K,, as a function of the modulation period are fitted by a mean-field model and a dipolar interaction model respectively. The Kerr rotation angles Bk relax at room temperature, which could be attributed to the existence of shear stress due to lattice mismatch at the interface.

Kerr rotation angle 6Jk of TbFeCo films thinner than 100 nm increased from 0.39 deg. to 0.54 deg. after depositing A1 films onto them. Such an increase of Ok is discussed with the enhancement of magneto-optical effect and the other mechanisms.

In this paper we study a motion of a rigidly rotating Nambu-Goto test string in a stationary axisymmetric background spacetime. As special examples we consider rigid rotation of strings in a flat spacetime, where explicit analytic solutions can be obtained, and in the Kerr spacetime.