In general relativity , the gyromagnetic ratio for all stationary , axisymmetric and asymptotically flat Einstein-Maxwell fields is known to be g = 2 .
In this paper , we continue our previous works of examination this result for rotating charged spacetimes with asymptotic non-flat structure .
We first consider two instructive examples of these spacetimes : The spacetime of a Kerr-Newman black hole with a straight cosmic string on its axis of symmetry and the Kerr-Newman Taub-NUT ( Newman-Unti-Tamburino ) spacetime .
We show that for both spacetimes the gyromagnetic ratio g = 2 independent of their asymptotic structure .
We also extend this result to a general class of metrics which admit separation of variables for the Hamilton-Jacobi and wave equations .
We proceed with the study of the gyromagnetic ratio in higher dimensions by considering the general solution for rotating charged black holes in minimal five-dimensional gauged supergravity .
We obtain the analytic expressions for two distinct gyromagnetic ratios of these black holes that are associated with their two independent rotation parameters .
These expressions reveal the dependence of the gyromagnetic ratio on both the curvature radius of the AdS background and the parameters of the black holes : The mass , electric charge and two rotation parameters .
We explore some special cases of interest and show that when the two rotation parameters are equal to each other and the rotation occurs at the maximum angular velocity , the gyromagnetic ratio g = 4 regardless of the value of the electric charge .
This agrees precisely with our earlier result obtained for general Kerr-AdS black holes with a test electric charge .
We also show that in the Bogomol ’ nyi-Prasad-Sommerfield ( BPS ) limit the gyromagnetic ratio for a supersymmetric black hole with equal rotation parameters ranges between 2 and 4 .