# How does a warp field interferometer work?

Assume I have a solid grasp of undergraduate physics. From what I've read the warp field interferometer is supposed to be a sort of Michelson interferometer, except instead of adjusting the displacement of one mirror, you have a toroidal capacitor that... somehow expands space?

Edit: I am talking about the work of Harold White at NASA. He's been apparently working on a way to implement an Alcubierre drive by generating a negative energy density with a torus of positive energy (but I don't know how this would work).

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NASA paper. Yes I am serious, at least in wanting to know how it works. – Mike Flynn Dec 11 '12 at 2:40
Having that link in the original post would have helped. – dmckee Dec 11 '12 at 3:19
warp drives a la alcubierre will not work as intended even with exotic matter because the equation requires the matter to be lied down first over a space-like region, before the space-like region can be used as a tunnel. The most likely outcome is that they won't find anything. But! Maybe they find something entirely different. – lurscher Dec 11 '12 at 3:21
After much Googling I've been unable to find an article describing the metric of a toroidal charge. If anyone knows of such an article I'd be interested to see it. – John Rennie Dec 11 '12 at 8:04
@twistor59, i added an answer a while ago with a reference on this site but i can't find it now. But the argument is pretty simple: Alcubierre starts with its goal metric and obtains the desired $T_{\mu \nu}$ that will provide it. But the boundary between the space-like warped region and previous times must have nonzero density. This happens everywhere along the space-like warped region. The conclusion that is reached is that the exotic density must be there first (at the same time, on all the Krasnikov tube), and only then, the warp is created – lurscher Dec 11 '12 at 12:53

The mentioned NASA paper have the answers, but it's too brief and may be difficult to follow. I recommend to read White' earlier paper http://dx.doi.org/10.1063/1.2169323 It has a nice explanation along with mathematics.In short it applies the Chung-Freese metric to the Alcubierre solution. The result is that the toroidal positive energy density could yield a spherical negative pressure region. So, it requires no negative energy or exotic matter. But these results are highly speculative and should be proven yet.

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