All Questions
Tagged with cosmology dark-matter
265
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$\Lambda$CDM's observations and the universe's matter content
It's known that the current value of the universe's total density parameter $\Omega_0=1$.
According to the $\Lambda$CDM model, the current density parameter of baryonic matter $\Omega_P \sim 0.04$, ...
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103
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Have information bits a mass-energy equivalence? [closed]
Is it plausible (as some authors conjectured recently) that information is physical and that information bits are stored as a mass-energy equivalent in the universe, accounting for cosmic dark energy ...
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237
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Can gravitational effects from past matter that you're looking at lightyears away produce an incorrect image of it? [closed]
Can gravitational effects from past matter that you're looking at lightyears away produce an incorrect image of it?
During the period that light from distant matter is travelling back to earth, can ...
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267
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Does anyone really know how dark energy/matter works?
If dark energy has no physical interaction with normal matter but it does interact with dark matter, wouldn't that cause an interaction with normal matter through its interaction with dark matter and ...
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How did neutrinos eliminated from dark matter? [duplicate]
I am reading "Dark Matter and Dark Energy" by Brian Clegg.
In Chapter 3 it's discussing about cosmic microwave background radiation and the elliptical shape
of early universe obtained from ...
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The scale factor of $\Lambda$CDM as a function of time
From Friedmann equation for flat universe:
$$
\left(\frac{\dot{a}}{a}\right)^2= \frac{8\pi G}{3} ~~ \left( \rho_m + \rho_r + \rho_\Lambda \right),
$$
can we simply get the scale factor $a$ as a ...
- 395
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114
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How to test for possible negative mass of dark matter?
What is the phenomenology of how to test if dark matter has possibly a negative mass (WP negative mass) in particle physics experiments, cosmology or astrophysics?
I lately came across this ...
- 4,170
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Could dark matter be just a gravitational effect of dark energy?
I'm wondering if we just looking at the two sides of the same coin and if there is actually a correlation of DM with DE?
Is it possible that DM just to be a gravitational effect (or an effect that ...
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Dark matter and un-smoothness in spacetime [duplicate]
Since dark matter currently is only observable with its gravitational effects and nothing else can we theorize that dark matter is only non-smoothness in spacetime that has been there from the Big ...
4
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1
answer
190
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How do BAOs provide evidence for dark matter?
So far my understanding of BAOs is that they are a relic of the old universe formed by the freezing of acoustic density waves in baryonic matter as the universe entered the recombination epoch. These ...
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$Ω = ρ/ρ[c]$, so although near to 1, for an accelerating expansion $Ω$ must be below 1. What's its value?
$Ω$ is taken to have different components - ordinary matter, dark matter, dark energy. But because it is expressed in relation to the critical density for attractive gravity, it seems that omega is ...
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3
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Why is the ratio of dark matter to normal matter larger in galaxies than the cosmic average?
There seems to be a discrepancy between the ratio of dark matter to normal matter in the Universe (about 5 to 1 according to $\Lambda$-CDM) and the ratio of the average dark matter halo mass to the ...
- 185
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Is there data regarding the large-scale density (mass/volume) of “dark matter plus ordinary matter,” as a function of time?
Here, large-scale means (conceptually) the known universe. Hopefully, the data runs from (perhaps somewhat after) the Big Bang until now. Pointers to such results would be appreciated.
5
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387
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Gravitational binding energy as alternative to dark matter?
Pondering this question: Casimir effect and negative mass
and, in particular, the response of John Rennie "as the mass of any bound system is slightly less than the mass of its parts" I ...
- 113
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Dark matter/dark energy in Einstein's equation as manifestations of entropy production
It is well known that pressure adds a contribution to the gravity sources in Einstein's equation. That contribution is unknown in Newton's theory. What about entropy itself, or more precisely the ...
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