Uncovering the Radiation of Cosmological and Black Hole Horizons

In summary, the conversation discusses the idea that not only black hole horizons, but also cosmological horizons, can radiate thermal energy. This is due to the accelerated expansion of the universe, which stretches quantum vacuum modes and can lead to the creation of particles. This concept is linked to the holographic principle and the cosmological constant. The temperature of the cosmological horizon is related to the acceleration of the expansion, and there is speculation about the relationship between virtual particles and spacetime in this context.
  • #1
Naty1
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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.
 
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  • #2
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.
 
  • #3
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.
 
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  • #4
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.
 
  • #5
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.
 
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  • #7
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?
 
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  • #8
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 ?
 
  • #9
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].
 

1. What is radiation from cosmological and black hole horizons?

Radiation from cosmological and black hole horizons is a form of energy that is emitted from the boundary or edge of a black hole or the observable universe. This radiation is thought to be the result of quantum fluctuations near the horizon of a black hole or during the expansion of the universe.

2. How is this radiation detected?

This radiation is extremely difficult to detect directly, as it is very weak and often obscured by other sources of radiation. However, scientists can indirectly observe its effects through changes in the temperature and density of the surrounding environment, as well as the behavior of matter and particles near the horizon.

3. What is the significance of uncovering this radiation?

Uncovering this radiation can provide valuable insights into the behavior and nature of black holes and the universe itself. It can also help to test and refine theories about the fundamental laws of physics, such as quantum mechanics and general relativity.

4. How does this radiation impact our understanding of the universe?

The existence of this radiation challenges our current understanding of the universe and can potentially lead to new discoveries and theories in the field of astrophysics. It also sheds light on the complex and mysterious nature of black holes and their role in the evolution of the universe.

5. What are some current research efforts in this area?

Scientists are using a variety of techniques and technologies, such as telescopes, detectors, and computer simulations, to study and uncover the radiation from cosmological and black hole horizons. They are also conducting experiments and observations to test different theories and models about this phenomenon.

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