Hawking Radiation w/out black holes

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Discussion Overview

The discussion centers around the concept of Hawking radiation and its potential existence outside of black hole horizons, particularly in various space-times. Participants explore the implications of Hawking radiation in contexts beyond astrophysical black holes, including the possibility of its occurrence in simpler systems like planets and the nature of temperature associated with Hawking radiation at distances from event horizons.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant references an article suggesting that Hawking radiation is not limited to black hole horizons and questions whether it can exist in space-times without black holes, such as around planets.
  • Another participant clarifies that the referenced paper discusses analog Hawking radiation in acoustical systems, not actual Hawking radiation from black holes, and explains the concept of a "dumb hole."
  • A participant acknowledges the distinction made in the paper but reiterates their interest in the broader question of Hawking radiation in various space-times.
  • One participant suggests that the study may relate to analogs of white holes rather than black holes, noting the generality of event horizons in general relativity (GR).
  • A reference to "Hawking-like flux" is made, indicating a potential variation or related concept in the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of Hawking radiation outside of black holes, with some supporting the idea of its existence in other contexts and others focusing on the specific nature of analog systems. The discussion remains unresolved regarding the broader implications of Hawking radiation in non-black hole scenarios.

Contextual Notes

There are limitations in the discussion regarding the definitions of Hawking radiation and its analogs, as well as the specific conditions under which these phenomena may occur. The relationship between event horizons and different types of gravitational systems is also not fully explored.

Pengwuino
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I stumbled upon an article while doing some research that had a statement saying that Hawking radiation can be found in places beyond black hole horizons. This lead me to this paper (which I'm not actually interested in beyond it's reference to the existence of hawking radiation outside of gravity) about observed Hawking Radiation in lasers

http://arxiv.org/abs/1009.4634

So apparently Hawking radiation is not simply confined to black hole horizons. The question I have, however, is if Hawking radiation exists in space-times that do not have astrophysical black holes. For example, can a simple planet exhibit hawking radiation? Also, even if you do have a black hole, does the Hawking temperature only apply to the horizon? That is, can the area an appreciable distance away from the event horizon have a temperature as seen from an observer at infinity?
 
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Pengwuino said:
http://arxiv.org/abs/1009.4634

This isn't a paper about Hawking radiation, it is a paper about analog Hawking radiation. Experimental physicists can't study Hawking radiation from black holes, so they study acoustical systems that have similar properties. In acoustical systems, a black hole analog is a region from which sound waves cannot propagate, and is called a dumb hole. The above paper is about optical systems. A detailed explanation of the paper is given at

http://physics.aps.org/articles/v3/95.
 
Yes, I'm aware, that's why I put the blurb about not being interested in the paper other than the brief mention that Hawking radiation is not something that only ever happens at the event horizon of a black hole.

So my question really truly is about space-time hawking radiation.
 
Cool paper! I don't pretend to understand all the optics and condensed-matter physics.

It sounds like what they're studying isn't an analog of a black hole, it's an analog of a white hole. (In GR, they aren't really different things, but I imagine that doesn't apply here.)

Event horizons in GR are much more general than black holes. For example, an accelerated observer has an event horizon: http://www.lightandmatter.com/html_books/genrel/ch06/ch06.html#Section6.1
 
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