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Dear James!

What happens if a gravitating object rotates is the so-called *drag
effect*. This is easiest to explain using a spherical body (e.g. a
star). When the star is nonrotating, a test mass (a small body) which is
shot into the direction of the centre of mass of the star will stay on a
straight trajectory (on a `radius'). With a rotating star, this is not the
case any more. The rotation somehow manages to `drag along' spacetime
around it so that the test mass would deviate slightly from the straight
line path
and take a course into the direction of the rotation.

As you might know, gravity obeys Einstein's Field equations, and every
solution of those equations might potentially be realized in the `real
world'. The solution of the field equations for a spherical, rotating body
is known as the `Kerr solution', and it predicts the mentioned drag effect.
I'm not sure whether the solution for a torus is known (at least I wasn't
able to find anything in that direction), but I'm quite sure that the drag
effect will take place anyway. After all one can show that *any* mass
distribution of finite extension will more or less look like a point mass
(or a sphere) the farther away you are, but the information about angular
momentum must not be lost.

Hope that helps,

Georg.

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