Gravitomangetic B-field units

Hi stubby,

can you give a reference to put this in context ? I don't know about GEM but in GR the field around a rotating body will induce rotation in test bodies. See Hamilton and Lyle arXiv:gr-qc/0411060v2.

M

 

There are various different conventions for the gravitomagnetic B-field, differing by factors of 2. However, they all effectively represent an angular velocity. Basically, if you are in such a field, you feel as if you are rotating, in the same way as if you're in the E-field component, you feel as if you are accelerating. The rotation can be detected for example by rotational frame-dragging of a gyroscope.

The gravitomagnetic equations can't be matched up exactly with the electromagnetic equations; one way or another there's always a factor of 2 needed somewhere, and different sources use different conventions. (Last time I looked, the Wikipedia entry on the subject was not even self-consistent). This does seem to relate to the need to use a tensor rather than a vector as part of the description of the force between relatively moving objects. However, I don't personally know how this relates to "spin 2".

For more details on GEM, I suggest you Google "gravitomagnetism" and have a look at the 2000 review paper by Mashhoon. There seems to be a more recent paper too, but I haven't looked at that.