Uncovering the Radiation of Cosmological and Black Hole Horizons

  • Context: Graduate 
  • Thread starter Thread starter Naty1
  • Start date Start date
  • Tags Tags
    Cosmological Horizon
Click For Summary

Discussion Overview

The discussion centers on the radiation associated with cosmological horizons and black hole horizons, exploring theoretical implications and the nature of thermal radiation in these contexts. Participants examine concepts from quantum mechanics, general relativity, and string theory, with a focus on the potential thermal effects observed by stationary observers near these horizons.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants note that Leonard Susskind claims the cosmological horizon radiates inward, potentially leading to infinite temperature as one approaches a black hole horizon.
  • Others discuss the holographic principle, suggesting that an observer inside a black hole may perceive thermal radiation due to their acceleration relative to a surface screen.
  • A participant expresses uncertainty about the applicability of these ideas to observers inside black holes or cosmological horizons.
  • There is a suggestion that the cosmological horizon appears "hot" due to its acceleration away from observers, raising questions about the direction of acceleration and its effects on observations.
  • References to a video by Verlinde indicate that the cosmological horizon has a temperature related to the cosmological constant and acceleration, suggesting a connection between expansion and particle creation.
  • Some participants speculate on the relationship between virtual particles and spacetime, questioning whether virtual geometries could become real as the universe expands.
  • One participant describes how accelerated expansion in a de Sitter universe leads to a temperature due to the stretching of quantum vacuum modes, linking this to gravitational particle production.

Areas of Agreement / Disagreement

Participants express a range of views regarding the nature of radiation from cosmological and black hole horizons, with no clear consensus on the implications or interpretations of the theories discussed. Multiple competing perspectives remain, particularly regarding the relationship between virtual particles, spacetime, and thermal radiation.

Contextual Notes

Some claims depend on specific interpretations of quantum mechanics and general relativity, and there are unresolved questions regarding the mathematical underpinnings of the proposed mechanisms. The discussion also highlights the complexity of relating theoretical concepts to observable phenomena.

Naty1
Messages
5,605
Reaction score
40
Here I had been thinking the Unruh horizons and specifically black hole horizons were the only (thermal) radiators.

Now I notice Leonard Susskind says in THE BLACK HOLE WAR that the cosmological horizon also radiates...but "inward" towards us. If a thermometer on a string were extended close to the cosmological horizon, he says "...we would discoverer the temperature increases eventually approaching the infinite temperature at the horizon of a black hole..."

What do you think??

If that's accepted or at least a rational theoretical idea, would a suspended (stationary) observer inside a black hole horizon also observe such radiation...thermal type? Seems like one would but I've never seen that stated anywhere.
 
Physics news on Phys.org
Susskind is an advocate of the holographic principle in the String Theory. His idea is different than this of Hawking. Each volume is surrounded by its surface and this surface contains all information contained in that volume. Therefore the inside observer is just a part of the hologram created by the surface's screen. If the observer sees a thermal radiation it means due to Davies-Unruh he is in an accelerating motion relative to that screen or eqivalently his apparent horizon increases.
I am not sure if it is correct. May be a professional physicist can write it properly.
 
czes: yes, in general that's correct...but I am not so sure about inside a black hole or cosmological horizon...butI think the same ideas hold...Hawking is a relativisit, Susskind a quantum/string theory oriented physicst.
 
Last edited:
Seems like with Unruh and Black hole horizon heat, the observer must accelerate; with the cosmological horizon, seems like it's accelerating away from any observer...it's doing all the work...so seems even more likely it would appear "hot".

And makes me wonder about my inside a black hole question...direction of acceleration relative to a horizon matters in such observations.
 
By dumb luck I stumbled across this Verlinde video...

http://streamer.perimeterinstitute.ca/mediasite/viewer/NoPopupRedirector.aspx?peid=37ff156a-33d5-40d8-9986-d5ec82d96d91&shouldResize=False#

At minute 4:30 it shows the temperature of the cosmological horizon [in Desitter space] and Verlinde mentions as I suspected that it's the " cosmological constant" ...acceleration... ...that underlies the temperature...

So it seems the cosmological horizon does indeed radiate...it HAS a temperature.
 
Last edited by a moderator:
Naty1 said:
By dumb luck I stumbled across this Verlinde video...

http://streamer.perimeterinstitute.ca/mediasite/viewer/NoPopupRedirector.aspx?peid=37ff156a-33d5-40d8-9986-d5ec82d96d91&shouldResize=False#

At minute 4:30 it shows the temperature of the cosmological horizon [in Desitter space] and Verlinde mentions as I suspected that it's the " cosmological constant" ...acceleration... ...that underlies the temperature...

So it seems the cosmological horizon does indeed radiate...it HAS a temperature.

So mere expansion is creating real particles, particles responsible for the temperature? I thought the cosmological constant was the zero point energy of virtual particle fields.

It sounds like we have spacetime popping into and out of existence right along with virtual particles. It sounds like one is made of the other. Are there virtual spacetime geometries popping into and out of existence, a portion of which become real as the universe expands?
 
Last edited by a moderator:
friend said:
So mere expansion is creating real particles, particles responsible for the temperature? I thought the cosmological constant was the zero point energy of virtual particle fields.

It sounds like we have spacetime popping into and out of existence right along with virtual particles. It sounds like one is made of the other. Are there virtual spacetime geometries popping into and out of existence, a portion of which become real as the universe expands?

The virtual particle-antiparticle lives to short to be observed. Therefore there is a vacuum made of virtual particles-antiparticles.
What if the virtual particle-antiparticle pair interact with an another pair in that very short time ? It could be in very strong gravitational field (Black Hole) or at gamma ray or at relativistic collision in accelerator. Is it possible that such a permanent relation creates a real particle and antiparticle ?
 
The reason that a de Sitter universe has a temperature is because of the accelerated expansion: comoving distances grow at a faster rate than the Hubble radius. The wavelength of quantum vacuum modes stretch along with the background, eventually surpassing the causal horizon. This is the mechanism by which inflation generates large scale fluctuations -- from gravitational particle production. If one simply starts with a free scalar field and drops it in de Sitter space, one finds that there is indeed a nonzero autocorrelation function [tex]\propto H^2/2\pi[/tex].
 

Similar threads

Graduate The CC and cosmological event horizon radiation
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Supressing black hole evaporation?
  • · Replies 15 ·
Replies
15
Views
4K
Undergrad Evaporating black holes and conservation of charges?
  • · Replies 14 ·
Replies
14
Views
4K
Undergrad Photon behaviour across EH threshold
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad The evaporation of charged black holes
  • · Replies 8 ·
Replies
8
Views
4K
Undergrad String theory calculation of Extremal black hole entropy problem
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad DeSitter cosmological horizon stability?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Two recent tests of loop quantum gravity theory
  • · Replies 15 ·
Replies
15
Views
6K
Graduate A Proposed Black Hole Entropy Calculation
  • · Replies 21 ·
Replies
21
Views
6K
Undergrad I don't see how a black hole's event horizon can be crossed
  • · Replies 73 ·
3
Replies
73
Views
4K