Do particles leave behind an image when crossing cosmo event horizon?

[Happiness]

TL;DR Summary

When particles cross the event horizon, can we still get information, such as their mass/charge, from the horizon? The information is available for how long? Is it still available after Hawking radiation has "returned" the particle back to the observable universe?

When objects/galaxies (particles and antiparticles) move across the cosmological event horizon, do they leave behind an “image” on the horizon, such that when we look at the image, we can tell what kinds of objects went through to the other side (ie, we would know information such as the mass and charge of the objects)?

If an object of, say, 5 kg moves across the cosmological event horizon, is it true that Hawking radiation (from the horizon) would “return” 5 kg of matter back to the observable universe over time? Therefore, would it be correct to say that conservation of mass/charge/energy/momentum/angular momentum/spin all holds true in the observable universe (taken as a whole) over time (apart from the gain in energy due to the gain in dark energy from the expansion of the universe)?

And when Hawking radiation has finished returning the 5 kg of matter (that was lost previously to the other side of the horizon), does the “image” of the original object then disappear from the horizon (surface)?

Do answers to the above apply equally to the black-hole event horizon too?

 

[PeterDonis]

When objects/galaxies (particles and antiparticles) move across the cosmological event horizon, do they leave behind an “image” on the horizon

No.

If an object of, say, 5 kg moves across the cosmological event horizon, is it true that Hawking radiation (from the horizon) would “return” 5 kg of matter back to the observable universe over time?

No.

would it be correct to say that conservation of mass/charge/energy/momentum/angular momentum/spin all holds true in the observable universe

No.

when Hawking radiation has finished returning the 5 kg of matter (that was lost previously to the other side of the horizon), does the “image” of the original object then disappear from the horizon (surface)?

There is no "image". See above.

Do answers to the above apply equally to the black-hole event horizon too?

In the sense that all of the answers are still "no", yes.

 

[Bandersnatch]

You can't ever see anything cross either kind of the event horizon, just approach it. The longer you wait, the closer it gets, but never reaches the horizon. So the question is moot.

 

[PeterDonis]

the question is moot

The very general question is not quite moot, at least as far as seeing effects of objects falling into a black hole. You can detect an increase in the mass of the hole. But you can't tell anything about what kind of object fell in if you don't have information from that object prior to its falling in.

 

[Happiness]

You can't ever see anything cross either kind of the event horizon, just approach it. The longer you wait, the closer it gets, but never reaches the horizon. So the question is moot.

I see. Then how does Hawking radiation come into play? Does a particle just move closer and closer to the horizon until one day it just disappears and is re-emitted instantly from another region (that is very close to the horizon)? And it's emitted with a velocity different from its original velocity such that it now moves towards us (away from the horizon)? I mean, how does this particle that never reaches the horizon give rise to Hawking radiation?

 

[PeterDonis]

how does Hawking radiation come into play?

It gets radiated out over very, very long time scales. Eventually, the entire hole has radiated away, and in the final burst of radiation before it is completely gone, you could in principle see images of objects that crossed the horizon. But you won't see anything from inside the horizon.

Does a particle just move closer and closer to the horizon until one day it just disappears and is re-emitted instantly from another region

No.

And it's emitted with a velocity different from its original velocity such that it now moves towards us (away from the horizon)?

No.

how does this particle that never reaches the horizon give rise to Hawking radiation?

Nobody said the particle doesn't reach the horizon (and fall on inward). @Bandersnatch just said you can't see the particle reach the horizon. The fact that you can't see it (at least not until the hole finally evaporates--see above) does not mean it doesn't happen.

 

[PeterDonis]

@Happiness you appear to have a very faulty mental model of how black holes, cosmological horizons, and Hawking radiation work. What sources have you studied?

 

[Vanadium 50]

In the sense that all of the answers are still "no", yes.

In a 1960s science fiction TV show this sentence would cause a computer to explode.

 

[Vanadium 50]

cosmological event horizon,

Di you mean "cosmological horizon" or a black hole's "event horizon". They are not the same thing.

 

[Bandersnatch]

There's more than one horizon in cosmology, and the one in question is also called event horizon. Cosmological event horizon is correct usage.

 

[Happiness]

It gets radiated out over very, very long time scales. Eventually, the entire hole has radiated away, and in the final burst of radiation before it is completely gone, you could in principle see images of objects that crossed the horizon. But you won't see anything from inside the horizon.

Does cosmological event horizon radiate until it is completely gone too? Black holes can do that because they can shrink until they vanish. But for cosmological event horizon, the "hole" is outside of the spherical surface that is the event horizon (and we are inside the sphere). So I cannot imagine how the "outside" of the sphere could shrink till it vanishes. It only makes sense in the case of black holes, when the holes are inside the spheres. But when the hole is outside, I have difficulty visualizing how it could shrink till it vanishes.

 

[Happiness]

@Happiness you appear to have a very faulty mental model of how black holes, cosmological horizons, and Hawking radiation work. What sources have you studied?

I am now studying quantum mechanics. Cosmology, not much, just read a bit here and there. I've watched Leonard Susskind's lectures on cosmology, but that was quite some time ago. Do you have a good resource to recommend that is related to my question?

 

[PeterDonis]

Does cosmological event horizon radiate until it is completely gone too?

No.

 

[PeterDonis]

Do you have a good resource to recommend that is related to my question?

Your question is about a very advanced topic, where we do not even have theories that are generally accepted and we do not have any prospect of doing relevant experiments now or in the foreseeable future. At the very least, you would need a good background in General Relativity and quantum field theory in curved spacetime. By "good background" I mean that you would have worked your way through, say, Wald's classic GR textbook and his 1993 monograph on QFT in curved spacetime and black hole thermodynamics and have been able to follow most of the material and work most of the problems.

 

[PeterDonis]

After moderator review, this thread is closed.