Unruh effect - When?

Main Question or Discussion Point

1. After some delay, because it takes time for the photons to travel from the Rindler horizon
2. Immediately, because an object instantly "assumes" an accelerating frame, which is already filled with Unruh radiation.

Thanks.

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Demystifier
Number 2.

Number 2.
So we detect Unruh radiation even if Rindler horizon is not visible - say, is obscured by something?

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That's logically the same as "Can I still see something when my hands are covering my eyes?"

That's logically the same as "Can I still see something when my hands are covering my eyes?"
What if your hands (screen) are far enough from you - almost at Rindler's horizon?
Then saying that distant screen blocks Unruh radiation is the same as claiming #1 in my first post.

Demystifier
So we detect Unruh radiation even if Rindler horizon is not visible - say, is obscured by something?
That's correct. The horizon is not essential for the Unruh effect. See e.g.
http://lanl.arxiv.org/abs/gr-qc/0103108 [Mod.Phys.Lett.A16:579-581,2001]

marcus
Gold Member
Dearly Missed
Thanks Demy! It's good to have that point clarified!
So (and please correct this if it's wrong) the temperature arises locally in the vacuum just from acceleration---and the Rindler horizon is a nonessential descriptive parameter of the acceleration?

Thanks also to Tzimie for asking the right question to elicit the clarification.

Demystifier
So (and please correct this if it's wrong) the temperature arises locally in the vacuum just from acceleration---and the Rindler horizon is a nonessential descriptive parameter of the acceleration?
That's almost correct, with a caveat that the effect is local in space (a very small detector can see the effect) but not completely local in time (in order for the detector response to have a thermal spectrum, the acceleration must exist for a long time).

Incidentally, today a new paper appeared which discusses these things in more detail:
http://lanl.arxiv.org/abs/1501.00119

marcus
Gold Member
Dearly Missed
That's almost correct, with a caveat that the effect is local in space (a very small detector can see the effect) but not completely local in time (in order for the detector response to have a thermal spectrum, the acceleration must exist for a long time).

Incidentally, today a new paper appeared which discusses these things in more detail:
http://lanl.arxiv.org/abs/1501.00119
Yes! I saw that and logged it on the biblio thread! Nicolaevici "Unruh effect without Rindler horizon"! just what you were talking about (and wrote about several years ago.

Thank you, and I am happy because my intuition was right :)
What's about radiation from the cosmological horizons in our expanding Universe? Do we need to see cosmological horizons or not?

Demystifier