arXiv subjects

Chandrachur Chakraborty

Publications and source records attributed to Chandrachur Chakraborty.

39 records · Page 3Linked to original sources

arXiv2014

Inner-most stable circular orbits in extremal and non-extremal Kerr-Taub-NUT spacetimes

We study causal geodesics in the equatorial plane of the extremal Kerr-Taub-NUT spacetime, focusing on the Innermost Stable Circular Orbit (ISCO),and compare its behaviour with extant results for the ISCO in the extremal Kerr spacetime. Calculation of the radii of the direct ISCO, its Kepler frequency, and rotational velocity show that the ISCO coincides with the horizon in the exactly extremal situation. We also study geodesics in the strong {\it non}-extremal limit, i.e., in the limit of vanishing Kerr parameter (i.e., for Taub-NUT and massless Taub-NUT spacetimes as special cases of this spacetime). It is shown that the radius of the direct ISCO increases with NUT charge in Taub-NUT spacetime. As a corollary, it is shown that there is no stable circular orbit in massless NUT spacetimes for timelike geodesics.

gr-qc↗

arXiv2013

Lense-Thirring Precession in Plebański-Demiański spacetimes

An exact expression of Lense-Thirring precession rate is derived for non-extremal and extremal Plebański-Demiański spacetimes. This formula is used to find the exact Lense-Thirring precession rate in various axisymmetric spacetimes, like: Kerr, Kerr-Newman, Kerr-de Sitter etc. We also show, if the Kerr parameter vanishes in Plebański-Demiański(PD) spacetime, the Lense-Thirring precession does not vanish due to the existence of NUT charge. To derive the LT precession rate in extremal Plebański-Demiański we first derive the general extremal condition for PD spacetimes. This general result could be applied to get the extremal limit in any stationary and axisymmetric spacetimes.

gr-qc↗

arXiv2013

Lense-Thirring precession in strong gravitational fields

An exact expression for the rate of dragging of inertial frames (Lense-Thirring (LT) precession) in a general stationary spacetime, is derived without invoking the weak field approximation. This expression, when used for the Kerr metric, leads to the LT precession frequency in the strong gravity regime appropriate to compact gravitating objects like rotating neutron stars and black holes. Numerical values of the precession rate are computed for a few known cases of pulsars (including a double-pulsar) and compared to the precession rates in the weaker gravity regimes of the earth and the sun.

gr-qc↗