All Questions
Tagged with cosmology event-horizon
63
questions
2
votes
3
answers
132
views
Can a light signal from Earth reach a galaxy outside the Hubble Horizon?
Is this video on the FLRW metric (timestamp 29:00 minutes) mistaken in its claim that a light signal from Earth cannot catch up with a galaxy outside the Hubble horizon, due to the horizon receding at ...
- 6,112
0
votes
1
answer
76
views
Black Hole Formation -- How Can an Event Horizon be Observed to Grow? [duplicate]
This is a question about black hole formation. To be clear, I’m not suggesting that black holes don’t form. It’s that I’m having trouble with the accepted explanation so there’s a flaw in my logic ...
- 21
2
votes
0
answers
30
views
Effects of quantum jitters at the event horizon?
General relativity would seem to have a black hole’s event
horizon be perfectly smooth on even the smallest scales.
Theorists studying black hole event horizons are aware of the
possibility of quantum ...
- 149
0
votes
1
answer
47
views
Electrons keeping dynamical quantum fluctuations?
I was thinking about this paper (https://arxiv.org/abs/1405.0298) where the authors argue that there wouldn't be dynamical quantum fluctuations in a De Sitter space as fluctuations would be static ...
- 2,462
1
vote
2
answers
72
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Hawking-like radiation will probably be difficult to detect (even if it can be detected). Why is that?
I was having a conversation in another physics forum about horizons (like the event horizon of a black hole, or a cosmological horizon) emitting Hawking radiation and I mentioned that if the universe ...
- 2,462
2
votes
0
answers
41
views
On entropy in a de Sitter horizon in a universe undergoing accelerated expansion?
I have a question about de Sitter cosmological horizons:
In this video by Leonard Susskind (https://youtu.be/n7eW-xPEvoQ?t=2324) he explains the concept of the Poincaré recurrence using particles and ...
- 2,462
0
votes
0
answers
45
views
What is the difference between the cosmological and the black hole horizons in thermodynamics?
I want to know the different thermal behaviors between cosmological and black hole horizons, such as temperature, entropy and so on.
- 113
2
votes
1
answer
148
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Negative $\Lambda$ FLRW spacetimes as infinite black holes?
Consider the Friedmann equation:
$$H^2+\frac{k}{a(t)^2} = \frac{\Lambda}{3}+\frac{8 \pi}{3}\rho$$
and set the parameters for dust in either flat euclidean or open hyperbolic spatial slices with a ...
- 125
1
vote
1
answer
60
views
Cosmological horizon and Hawking/Unruh radiation? [closed]
I have two questions about cosmological horizons and their emission of radiation
The first one is:
There are some authors that propose that dark energy or the accelerated expansion of the universe ...
- 2,462
3
votes
1
answer
307
views
Cosmological understanding from Penrose diagram of de Sitter spacetime
The conformal diagram of de Sitter spacetime looks like this
I think I understand the causal properties of this diagram. Someone who is static in the south pole can send messages only to the upper ...
- 4,827
1
vote
1
answer
109
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Does the current size of the cosmological sound horizon play a relevant role in the universe?
I am doing some interactive plots about cosmological horizons and in my research I stumbled upon the sound horizon, the baryonic acoustic oscillations and how it had an impact on the formation of the ...
0
votes
1
answer
191
views
Are black holes the edge of our universe?
Are black holes the actual edge of the universe? Because spacetime is another dimension, I would assume the universe doesn’t have perceived corners or edges. At least humans cannot perceive it.
The ...
- 11
3
votes
0
answers
61
views
Hypothetically, could the interior of a black hole look exactly like the universe that surrounds us?
I do understand that we can't experimentally verify anything we imagine about the interior of a black hole.
If we were to apply what we know about the physics of the observable universe and assume ...
- 33
1
vote
0
answers
22
views
Big Crunchs and Event horizons [duplicate]
There are Two different defintions for the event horizon of a black hole.
The Absolute horizon and the Apparent horizon.
An apparent horizon is a surface that is the boundary between light rays that ...
- 2,908
0
votes
1
answer
138
views
When will the particle horizon reach its limit of 63 billion light years?
In the far future, the particle horizon will reach 63 Gly，so when will that time? Just like today's universe time is 13.82 Gyr and the particle horizon is 46.5 Gly, how many years will the particle ...
