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MEMS Researchers Hope To Exploit Casimir Effect
smartalix writes "Researchers at Purdue University's School of Science are examining the Casimir effect (a phenomenon that explains Max Planck's and Werner Heisenberg's quantum vacuum fluctuation theory) and its impact on nanostructures in MEMS devices. At the distances these structures such as gear teeth, actuators, and such) will be operating from one another, the Casimir force may become something to reckon with, potentially forcing a limit to the level of miniaturization possible. The Purdue team is not only confirming Casimir's original theory, it is exploring possible ways to harness the effect in micromachines."
It comes from the fact that in curved spacetime there is no natural choice of time coordinate and so you can't distinguish between positive and negative energy modes meaning that you can't distinguish properly between creation and annihilation operators.
The answer to that's not so clear: it's true the number operator in different (curved) reference frames is different, since the annihilation/creation operators are different. However, saying that has nothing to do with pair-production isn't exactly correct - after all, the zero-point energy, in some cases, generates from normal-ordering (a adagger + adagger a) (in others from symmetry breaking, but I think the same argument applies). You could in fact, define ZPE = integral (adagger a - a adagger), which gives you something like ZPE = integral (N - Ndagger). ZPE density would just be N - Ndagger, and could be interpreted as the number of virtual particle pairs created per unit space per unit time.
Bleh, that's hard to understand without writing things down. Anyway, the point is that if you consider "ZPE" to be "all of the virtual particle pairs in the quantum vacuum", then, for instance, Unruh radiation (and likely Hawking radiation as well) can be explained 'somehow' via virtual particle pairs, as Unruh radiation is just going to be the difference between N in one reference frame and N in another reference frame, hence ZPE in one reference frame, and ZPE in another reference frame. I mention Unruh radiation because it'd be harder to explain 'canonically' than Hawking radiation, though I can somewhat see a way to explain it.
What the actual 'canonical explanation' is, that's a different story. It doesn't tremendously matter, as virtual particle pairs don't appear as two little balls zipping through space at all. It's just a picture for the minds' eye. However, basically saying that the curved spacetime produces a change in particle pair production/destruction rate from one reference frame to another, resulting in a generation of particles, that's perfectly valid, and so, the pair-production argument isn't totally bunk.