On Newman-Penrose constants of stationary electrovacuum spacetimes

A theorem related to the Newman-Penrose constants is proven. The theorem states that all the Newman-Penrose constants of asymptotically flat, stationary, asymptotically algebraically special electrovacuum spacetimes are zero. Straightforward application of this theorem shows that all the Newman-Penrose constants of the Kerr-Newman spacetime must vanish.Comment: 11pages, no figures accepted by PR

An explanation of the Newman-Janis Algorithm

After the original discovery of the Kerr metric, Newman and Janis showed that this solution could be ``derived'' by making an elementary complex transformation to the Schwarzschild solution. The same method was then used to obtain a new stationary axisymmetric solution to Einstein's field equations now known as the Kerr-newman metric, representing a rotating massive charged black hole. However no clear reason has ever been given as to why the Newman-Janis algorithm works, many physicist considering it to be an ad hoc procedure or ``fluke'' and not worthy of further investigation. Contrary to this belief this paper shows why the Newman-Janis algorithm is successful in obtaining the Kerr-Newman metric by removing some of the ambiguities present in the original derivation. Finally we show that the only perfect fluid generated by the Newman-Janis algorithm is the (vacuum) Kerr metric and that the only Petrov typed D solution to the Einstein-Maxwell equations is the Kerr-Newman metric.Comment: 14 pages, no figures, submitted to Class. Quantum Gra

Accretion of New Variable Modified Chaplygin Gas and Generalized Cosmic Chaplygin Gas onto Schwarzschild and Kerr-Newman Black holes

In this work, we have studied accretion of the dark energies NVMCG and GCCG onto the Schwarzschild and Kerr-Newman Black holes. We find the expression of the critical four velocity component which gradually decreases for the fluid flow towards the Schwarzschild as well as Kerr-Newman Black hole. We also find the expression for change of masses of the black hole in both cases. For the Kerr-Newman black hole which is rotating and charged we calculate the specific angular momentum and total angular momentum. We showed that in both cases due to accretion of the dark energy mass of the black hole increases and angular momentum increases in case of Kerr-Newman black hole.Comment: 12 pages, 14 figures, Accepted for publication in European Physical Journal

Spinning Higher Dimensional Einstein-Yang-Mills black holes

We construct a Kerr-Newman-like spacetimes starting from higher dimensional (HD) Einstein-Yang-Mills black holes via complex transformations suggested by Newman-Janis. The new metrics are HD generalization of Kerr-Newman spacetimes which has a geometry precisely that of Kerr-Newman in 4D corresponding to Yang-Mills (YM) gauge charge, but the sign of charge term gets flipped in the HD spacetimes. It is interesting to note that gravitational contribution of YM gauge charge, in HD, is indeed opposite (attractive rather than repulsive) that of Maxwell charge. The effect of YM gauge charge on the structure and location of static limit surface and apparent horizon is discussed. We find that static limit surfaces become less prolate with increase in dimensions and are also sensitive to YM gauge charge thereby affecting the shape of ergosphere. We also analyze some thermodynamical properties of these BHs.Comment: Accepted for publication in EPJ

Newman and conversion

Ker, Ian T. Newman and conversion. Edinburgh: T & T Clark; Notre Dame, Ind: Univ of Notre Dame Pr, 1997