Circular motion in NUT space-time

Abstract

Abstract. We consider circular motion in the NUT (Newman-Unti-Tamburino) space-time. Among other things, we determine the location of circular time-like geodesic orbits, in particular of the innermost stable circular orbit (ISCO) and of the marginally bound circular orbit. Moreover, we discuss the von Zeipel cylinders with respect to the stationary observers and with respect to the Zero Angular Momentum Observers (ZAMOs). We also investigate the relation of von Zeipel cylinders to inertial forces, in particular in the ultra-relativistic limit. Finally, we generalise the construction of thick accretion tori ("Polish doughnuts") which are well known on the Schwarzschild or Kerr background to the case of the NUT metric. We argue that, in principle, a NUT source could be distinguished from a Schwarzschild or Kerr source by observing the features of circular matter flows in its neighbourhood.

On some novel features of the Kerr–Newman-NUT spacetime

“…In this case as well, the conditions for circular orbit are given by V eff = 0 and V eff = 0, see Eq. (16). To see the existence of circular orbits in this spacetime in a direct manner, we have plotted the effective potential V eff , rescaled by (r 2 + l 2 ) −2 , for specific choices of various constants of motion and parameters appearing in the problem in Fig.…”

“…Thus a proper understanding of the geodesic motion in the presence of NUT parameter is essential. Following such implications in mind, there have been attempts to study circular timelike geodesics in presence of NUT parameter [14][15][16] 1 as well as motion of charged particles in this spacetime [17]. Various weak field tests, e.g., perihelion precession, Lense-Thirring effect has also been discussed [18][19][20] (for a taste of these weak field tests in theories beyond general relativity, see [21][22][23][24][25]).…”

“…Note that the results presented in[14,15] are based on the erroneous assumption that circular geodesics lie on the equatorial plane, see e.g.,[16] 2. Since it is well known that presence of rotation also produces gravomagnetic effects, it is not out of place to consider a relation between them.…”

Circular orbits in Kerr-Taub-NUT spacetime and their implications for accreting black holes and naked singularities

“…Because, setting a → 0 in eq. (35), one can check that the CPO can always occur at [2,48] r TN c → M 1 + 2(1 + n 2 * ) 1/2 cos 1 3 tan −1 (n * )…”

Nutty black holes in Galileon scalar-tensor gravity

“…In spite of the difficulty of finding a global definition of the NUT space-time, the solution possesses many remarquable properties, namely : (i) like the Kerr solution, it is stationary but non-static due to non-vanishing g tϕ metric terms ; (ii) it can be extended analytically (i.e. without curvature singularity) in the interior region by means of a TAUB solution.Likely for these reasons, several authors (see namely [19,20]) have considered the NUT parameter as a possible ingredient of some astrophysical object and have studied its effect on geodesics in NUT space-times. Another application of the NUT parameter was proposed recently in [21] to obtain families of non-trivial, spherically symmetric solutions of the Einstein-Chern-Simons gravity coupled to a scalar field.…”