inspired by https://lemmy.world/post/39777765
Unruh effect should work for any acceleration, including centripetal acceleration of a James Bond-style killer centrifuge/amusement ride. The "thermal bath" experienced by such an observer is composed mainly of photons, but also some elementary particles, in proportion to quantum field coupling strengths or something, coming in as a "particle shower" from the direction of the Rindler event horizon - namely down. The accelerated observer can capture these particles for use later. Did I get it all correct?
So I did a bit more reading. It seems like acceleration alone is not enough for invoking equivalence principle and saying we have Unruh radiation. If it was enough, non-blackholes objects would Hawking radiate like both of us were suspecting. Apparently physicists are quite confident only blackholes can Hawking radiate.
There is another picture that may work better for us. Instead of thinking of Unruh radiation (which would require doing serious QFT in curved spcetime calculations), we can think of the radiation coming from ripples popping up near the horizon (the black hole horizon for Hawking, the Rindler horizon for Unruh).
In this picture you absolutely need a horizon to get radiation. So on the centrifuge you won't feel any radiation ๐คทโโ๏ธ
Good to know! I was starting to get worried :D
Does the particle need to travel all the way from the horizon to reach you? How long does that take? The horizon still exists on the centrifuge, if only for a moment, shifting slightly from one instant to the next. In principle, at any moment you could detach from the centrifuge and fire 10g rocket thrusters in a straight line instead. In that first instant there is no way to tell the difference between the two.
I say this because in the linked paper, the "acceleration" experienced by the positrons was the bouncing off the atomic nuclei in the silicon crystal, which takes place over the space of a few angstroms, or at most within the 3.5mm size of the crystal, in the time given by the speed of 178GeV positrons (+Lorenz contraction). This instant was sufficient to claim Unruh effects were occurring.
Technically it's not really a horizon if it "opens up" allowing you to observe events from the inside afterwards. But of course in any realistic setting (including that experiment) it will open up eventually, so no horizon. But nature doesn't know that it will open up, so maybe it should behave like a horizon until nature knows, resulting in a criteria like you said. I think the criteria is loosely equivalent to saying "the acceleration must change the speed by almost c", so your centrifuge probably wouldn't lead to radiation.
But I really am not sure about any of this. The right way to do this is to actually calculate the mode function. One day when I'm better with QFT and all these stuff I'll try to do it.