Talk:Unruh effect

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Question: The last sentence, about testing the effect, mentions accelerating a particle to 10^26 m/s^2. How does that work? The only way I can figure is to keep oscillating its speed, since after the first second of uniform acceleration it would exceed lightspeed.

The acceleration is measured in the rest frame of the accelerating particle. Measured from an inertial frame, the acceleration would get smaller and smaller as the apparent mass of the particle increses with speed. If you have access to a physics library, check out the section on "hyperbolic motion" in Misner, Thorne and Wheeler's Gravitation; you can also look at Rindler's book Relativity: Special, General and Cosmological (renamed simply Relativity for the second edition). I would also recomend Taylor and Wheeler's Special Relativity. — Miguel 21:41, 2004 Dec 9 (UTC)
If I don't mix things up, we are talking about very short periods of accelaration, e.g. by using the electromagnetic field of laser light: http://www.slac.stanford.edu/slac/media-info/20000605/chen.html --Pjacobi 21:07, 9 Dec 2004 (UTC)
  • Edits Those last two "anon" edits (23 Oct 2005) were by me. Login-related Wikiglitches ( :( ) ErkDemon 20:13, 23 October 2005 (UTC)


I have a feeling this article would be really interesting if it was written in English. --61.214.155.14 04:41, 18 August 2006 (UTC)

This is as close to English as it's really possible to get. The first paragraph of the overview gives a pretty good layman's overview, and the rest of the introduction adds on detail incrementally. I can't completely follow the final parts of it, but I seriously doubt there's _any_ way to explain the detailed mechanism that doesn't require me to learn about the terms being used. The qualitative effect is covered in the first paragraph ("if you accelerate, it looks like space is filled with a warm gas instead of empty"), with no additional explanation needed.
If you can think of a better way this should be organized, by all means propose it here. --Christopher Thomas 05:09, 18 August 2006 (UTC)


What is "k"? "T" might be temperature, and "c" light celerity, "π" some times means the relation between radius ant its circumference, but what is "k"? Coronellian 19:09, 16 August 2007 (UTC)

I though this article means that the minimum temperature on hearth is 4×10−20 K, not 0 K. It is likely the sincrotron radiation, but only at 9.8 m/s2. Coronellian 19:17, 16 August 2007 (UTC)

[edit] Controversy

The existence of Unruh radiation is not universally accepted. Its status ranges from claims that it has already been observed[1], to claims that it is not emitted (although the sceptics accept that an accelerating observer thermalises at the Unruh temperature they do not accept that this leads to the emission of real photons. arguing that the emission and absorption rates are balanced in their model and, they claim, probably more generally)[2].

  1. ^ Photoluminescence from a gold nanotip as an example of tabletop Unruh-Hawking radiation
  2. ^ Is there Unruh radiation?


The controversy about emission is actually an old one--- does a uniformly accelerated charge radiate? The radiation reaction force is proportional to da/dt, so if a is constant, there is no radiation. But boundary effects make a big difference, and so the controversy.
The Unruh effect itself, though, doesn't care about outgoing photons. It only cares that the detector responds as if in a thermal bath. On that count, the sources you cite don't have any controversy, and as far as I know, nobody else does either. So I think it would be better to make this comment on "radiation reaction", or something.Likebox (talk) 12:14, 30 January 2008 (UTC)
Unruh radiation redirects to Unruh effect -- a distinction this section clearly makes -- so it is an issue for this article. End of story. --Michael C. Price talk 12:26, 30 January 2008 (UTC)
Ok, then I'll put it in, but try to be careful with the distinction.Likebox (talk) 14:48, 30 January 2008 (UTC)
I'm clear about the distinction. Let's make sure about the article. Thanks for reinserting it. If the sceptics are right then this has big implications for Hawking radiation... --Michael C. Price talk 21:13, 30 January 2008 (UTC)
I get your drift, but it's just the Unruh effect that's needed for the Hawking radiation, not the Unruh radiation. That's why I wanted to be so careful to make the distinction. You don't need to radiate real photons to infinity in the Rindler case to get the real photons coming out of the black hole. The big difference is that if you redshift in the Rindler metric, the redshift factor goes to 0 as rho->infinity, meaning that by the time you get to infinite rho the equilibrium state is zero temperature. This doesn't mean that Unruh radiation doesn't exist--- I haven't figured that out. I don't know if it does or doesn't I mean. There's other wedges and boundary conditions and I get confused. But in the Hawking case, When you match up the local observer temperature which you know from the local near-horizon Unruh effect to the far-observer temperature by redshifting, the redshift factor asymptotes to a finite value. So if the black hole has a vacuum state which matches to the Unruh vacuum near the horizon, it's got to be hot at infinity, while the Rindler space at infinity is cold no matter what. I'm still confused about the Rindler radiation thing though.Likebox (talk) 22:34, 30 January 2008 (UTC)