|MadSci Network: Physics|
James, Thanks for the question. General relativity is not a specialty of mine, but here are some thoughts on the rotating toroid. My first thought is that in one sense we already have this sort of thing going on in particle accelerators. Granted, the total mass contained in the toroidal volume of an accelerator is only about 10^-12 grams, but the velocity can be 99.9...% of light speed for these particles. There don't seem to be any noticeable space-time effects for this situation. For any noticeable GR type effects it seems a stellar amount of mass is necessary. The rotation of such a mass results in "frame dragging" or the Lense-Thirring effect. Space time is slightly twisted around massive spinning bodies. For the Earth, the effect is in the parts per trillion range. For the Sun, the effect may reach the parts per billion level. A very massive and dense body rotating a high frequency such as a black hole can create significant frame dragging. The accretion disk around a blackhole has been observed to wobble many times a second because of frame dragging. The general effect of frame dragging seems to be that energy is robbed from objects orbiting around the frame dragger, so that the orbits slowly decay. See: http://www.black-holes.com/ . There should not be a limit as to how much angular momentum, that is spin, can be given a blackhole. A spinning blackhole ( a Kerr type blackhole ) should have a toroidal singularity inside it. For such a blackhole, a particle inside the event horizon cannot escape, but it does not have to hit the singularity. If a blackhole spins fast enough, some think that the event horizon itself might become toroidal. IF this is possible, then a particle could fall through the center of the toroidal singularity without crossing the event horizon. What this might accomplish is debatable. Speculating, it seems like frame dragging effects should be noticeable in the center of a rotating object. This might then contribute to gravitational stresses at the center of a rotating object that would not be there if it was not rotating. Sorry that I cannot give you anything more specific. Toroidal blackholes have not been investigated much, at least on the Web, so far. I got most of my information from http://ourworld.compuserve.com/homepages/eric_baird/wh_home.htm. Best Regards, Everett
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