All Questions
Tagged with black-holes cosmology
215
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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 ...
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Calculating Gaussian Curvature for metric
I am trying to calculate Gaussian curvature of an optical metric
$$
d \sigma^2=\frac{r\left(\omega_{\infty}^2-\omega_e^2\right)+2 m \omega_e^2}{(r-2 m) \omega_{\infty}^2}\left(\frac{d r^2}{1-\frac{2 m}...
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Does the Schwarszchild solution require the cosmological constant to stop it from expanding?
When Einstein developed his field equations for general relativity, he attempted to apply them to the entire universe. He found the universe had to expand, which at the time was believed not to be the ...
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Probability of a primordial black hole absorbing background radiation?
I'm thinking of the early universe when there was a lot of energetic radiation around. A primordial black hole (PBH) that would be about to evaporate completely about now, would have an initial mass ...
- 5,571
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Test of the primordial black hole solution to dark matter
One of the ideas that might solve some of the dark matter problem are the existence of many small black holes. There is evidence, in principle, for the existence of these small black holes via the ...
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Trapping Hawking radiation in black holes?
I was reading this writing (https://davidwoolsey.com/AttO/AttO_blog/Entries/2020/7/13_Black_Holes_and_Transverse_Tidal_Effects%2C_a_revised_essay_on_some_thoughts.html) about considering tidal effects ...
- 2,466
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Angular momentum, black holes and up-tunneling events in the vacuum
To give some context on the matter, I found these interesting articles (https://arxiv.org/abs/2007.11428 & https://arxiv.org/abs/2003.04927) where the authors analyzed, among other things, the ...
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Could primordial black holes have been supermassive?
Usually when primordial black holes are mentioned, they are imagined to be tiny. Could they have been supermassive? This would explain the existence of quasars in early universe.
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Big Bang Escape Velocity
When our entire section of the universe was in a single hot dark dense state, right before our big bang, what was the escape velocity?
user394592
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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
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1
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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$$
and set the parameters for dust in either flat euclidean or open hyperbolic spatial slices with a ...
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How can micro black holes exist?
How could a micro black hole exist, when there is so little matter to produce the intense gravitational force required to crush matter to that extent? It takes the collapse of a supermassive star to ...
- 393
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46
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Ejected bodies, dynamical friction and dark energy?
I have a question after reading a couple of papers (https://arxiv.org/abs/1707.06220 and https://www.arxiv-vanity.com/papers/1102.0007/).
Here, the authors seem to indicate that when bodies like stars ...
- 2,466
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How fast would a hypothetical microscopic quantum black hole evaporate with an effective mass of two protons?
According to the analysis shown in this research here, see link the evaporation time can be calculated in seconds using this equation:
$$
\begin{array}{l}
t_{\text {evap }}=\left(\frac{5120 \pi G^2}{\...
- 4,170
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What is the state of matter-energy inside Black Holes? [closed]
Do we know absolutely nothing about what might be the state of matter-energy inside the black hole?
Are there existing theories or research that explore the possibility of a metastable vacuum inside ...
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