Angular momentum, magnetic moment, andg-factor in general relativity

The gyromagnetic ratio of rapidly rotating compact stars in general relativity

“…In that sense, the g-factor is a good indicator of the strength of the gravitational field in an insulating perfect fluid, but is little dependent on the angular velocity of the star. In our study, the value g = 2 seems linked only with the black hole solution but, from other works, [14], [15] and [11], one can see that this may depend on the total charge of the system. An important improvement of our work would be to allow for any charge of the system, that is compatible with the stationarity assumption and therefore allow for differential rotation, which may open new possibilities.…”

“…Qualitatively, both studies agree: for Q/M 1 and taking into account energy conditions, Pfister and King find that g varies between ∼1 for a low compaction parameter, and 2 in the collapse limit. With a similar kind of problem, Mustafa et al [11] found that g could reach values very close to 2, for the charge-to-mass ratio less than unity and the shell radius approaching the event horizon value.…”

“…Therefore, there may not exist any stationary configuration for Q/M too larger than 1: the electrostatic force would overcome the gravitational one and disperse particles. Moreover, Mustafa et al [11] have shown that, in the case of a slowly rotating charged shell, when Q/M > 1 there is no upper or lower bound on the value of the g-factor. Finally, in order to find an acceptable stationary solution for 0.01 Q/M < 1, one would have to satisfy both equations (7) and j t = χn B .…”

Gyromagnetic factor of rotating disks of electrically charged dust in general relativity

“…Pfister and King considered the case of a rotating charged mass shell [8]. Apart from generalising previous studies on this matter [9][10][11], they noticed that g ≈ 2 is extremely robust, in the sense that this value is obtained in a big part of the mass shell's parameter space.…”

The gyromagnetic factor in electrodynamics, quantum theory and general relativity

“…This has the simplifying consequence that gravitational and electromagnetic effects decouple, and one has to solve only the Maxwell equations on a rotationally disturbed Schwarzschild background in the first order of an angular velocity ω. For arbitrary mass and charge Briggs et al [40], and Mustafa et al [41] succeeded in solving the coupled Einstein-Maxwell equations, resulting from a rotational dipole perturbation of the Reissner-Nordström solution. Their discussion of the g factor was, however, limited to some special cases (such as the weak-field and the collapse limit, the extreme Reissner-Nordström case, and the weak-field limit of the overextreme Reissner-Nordström case), and to some fixed values of q/M.…”