Kerr Taub NUT Research Articles

Particle acceleration on the background of the Kerr–Taub–NUT spacetime

We study the collision of two particles with the different rest masses moving in the equatorial plane of a Kerr–Taub–NUT spacetime and get the center-of-mass (CM) energy for the particles. We find that the CM energy depends not only on the rotation parameter, a, but also on the NUT charge of the Kerr–Taub–NUT spacetime, n. Especially, for the extremal Kerr–Taub–NUT spacetime, an unlimited CM energy can be approached if the parameter a is in the range [1,2], which is different from that of the Kerr and Kerr–Newman black holes.

Particle motion and electromagnetic fields of rotating compact gravitating objects with gravitomagnetic charge

The exact solution for the electromagnetic field occuring when the Kerr–Taub–NUT compact object is immersed (i) in an originally uniform magnetic field aligned along the axis of axial symmetry (ii) in dipolar magnetic field generated by current loop has been investigated. Effective potential of motion of charged test particle around Kerr–Taub–NUT gravitational source immersed in magnetic field with different values of external magnetic field and NUT parameter has been also investigated. In both cases presence of NUT parameter and magnetic field shifts stable circular orbits in the direction of the central gravitating object. Finally we find analytical solutions of Maxwell equations in the external background spacetime of a slowly rotating magnetized NUT star. The star is considered isolated and in vacuum, with monopolar configuration model for the stellar magnetic field.

MODIFICATIONS TO BEKENSTEIN–HAWKING ENTROPY DUE TO ARBITRARY SPIN FIELDS

The modified entropy, due to massless quantum fields of arbitrary spin s≤2, of the Kerr–Taub–NUT black hole is evaluated. The appearance of logarithmic terms is demonstrated. The modified entropy can be reduced to the form proportional to the area of the event horizon. However, modified coefficient not only depend on the characteristics of the black hole but also on the spin of the fields.

Separability and Killing tensors in Kerr–Taub-NUT–de Sitter metrics in higher dimensions

A generalisation of the four-dimensional Kerr–de Sitter metrics to include a NUT charge is well known, and is included within a class of metrics obtained by Plebanski. In this Letter, we study a related class of Kerr–Taub-NUT–de Sitter metrics in arbitrary dimensions D⩾6, which contain three non-trivial continuous parameters, namely the mass, the NUT charge, and a (single) angular momentum. We demonstrate the separability of the Hamilton–Jacobi and wave equations, we construct a closely-related rank-2 Stäckel–Killing tensor, and we show how the metrics can be written in a double Kerr–Schild form. Our results encompass the case of the Kerr–de Sitter metrics in arbitrary dimension, with all but one rotation parameter vanishing. Finally, we consider the real Euclidean-signature continuations of the metrics, and show how in a limit they give rise to certain recently-obtained complete non-singular compact Einstein manifolds.

Algebraically special frequencies of NUT black holes

The algebraically special frequencies of Taub–NUT black holes are investigated in detail in comparison with known results concerning the Schwarzschild case. The periodicity of the time coordinate, required for regularity of the solution, prevents algebraically special frequencies to be physically acceptable. In the more involved Kerr–Taub–NUT case, the relevant equations governing the problem are obtained.

Gravitomagnetism in the Kerr–Newman–Taub–NUT spacetime

We study the motion of test particles and electromagnetic waves in the Kerr–Newman–Taub–NUT spacetime in order to elucidate some of the effects associated with the gravitomagnetic monopole moment of the source. In particular, we determine in the linear approximation the contribution of this monopole to the gravitational time delay and the rotation of the plane of the polarization of electromagnetic waves. Moreover, we consider ‘spherical’ orbits of uncharged test particles in the Kerr–Taub–NUT spacetime and discuss the modification of the Wilkins orbits due to the presence of the gravitomagnetic monopole.

Symmetries of cosmological Cauchy horizons with exceptional orbits

We show here that if an analytic space-time satisfying the vacuum (or electrovacuum) Einstein equations contains a compact null hypersurface with closed generators, then the space-time must have a nontrivial Killing vector field. This result is an extension of an earlier theorem, which required that the generators of the hypersurface must not only be closed, but in addition must satisfy a local product bundle (LPB) condition. This LPB condition (which is known to be violated in certain of the Kerr–Taub–NUT space-time models) is equivalent to the requirement that the generators must all be ordinary fibers of a Seifert fibration. We prove here that the LPB condition can be dropped. Thus we have stronger support for our conjecture that causality violations (as evidenced by Cauchy horizons) in cosmological solutions of the Einstein equations are essentially an artifact of symmetry, and are therefore nongeneric.