Questions tagged [dark-energy]
Dark energy is the unknown form of energy that drives the acceleration of the universe's expansion.
580
questions
0
votes
0
answers
73
views
Does spacetime move? With respect to what?
Can spacetime itself rotate along a body, like a black hole? Would it move like a wave?
- 495
-3
votes
1
answer
84
views
Can matter and light exist without the free space absolute vacuum?
According to the standard model of particle physics, is matter and light possible to exist without the existence of the omnipresent vacuum?
By "vacuum" here I mean the ideal perfect vacuum ...
- 4,170
-1
votes
2
answers
75
views
The speed of expansion of space in big freeze
In the case of big freeze, space expansion will be accelerating and there appears to be a lot of different phenomena occurring. However, in the case of big rip, the expansion is super-accelerating so ...
- 13
0
votes
0
answers
40
views
What exactly do astrophysicists mean when they say that the universe is expanding at an accelerated rate? [duplicate]
What exactly do astrophysicists mean when they say that the universe is expanding at an accelerated rate? Assuming that the universe is a sphere, do they mean that the radius of the universe increases ...
- 23
3
votes
2
answers
505
views
What is the longest detectable EM wavelength?
What is the longest detectable (by today's technology) EM wavelength? and is there a limit of the energy that those with longer wavelengths that we cannot detect can carry? can there be a galactic or &...
- 553
0
votes
1
answer
93
views
$w$CDM and quintessence
i was reading about alternative dark energy models and i stumbled across the concept of quintessence: a scalar field that should generate a dark energy component with a EoS parameter $w$ that varies ...
- 299
1
vote
0
answers
52
views
In the $\Lambda$CDM model, is the cosmological constant always interpreted as the vacuum energy contribution?
As in the title, in the $\Lambda$CDM model, is the cosmological constant always interpreted as the vacuum energy contribution? Or is the origin left open?
If I say that "it is usually ...
- 299
0
votes
1
answer
101
views
Why the Hubble parameter that is proportional to dark energy is squared in the Friedmann's equation?
I'm studying Alexander Friedmann's equation about the Hubble parameter and, thus, the time dependence of the cosmic scale factor varies as the matter density, ρ, and as the dark energy, Λ as shown in ...
- 73
3
votes
1
answer
479
views
Confusion regarding the cosmological constant
The value of the cosmological constant is:- $+2.036\times 10^{-35} ~\mathrm{Hz}^2$. What does it mean about the characteristics of our spacetime? What does the value of the cosmological constant tell ...
user355398
3
votes
1
answer
215
views
The energy conditions and cosmological constant?
So I thought it didn't matter which side of the equation the cosmological constant was one (did it emerge from geometry or the stress energy tensor). However, then I remembered the weak , strong, null,...
- 1,389
9
votes
2
answers
469
views
What does it mean that "relativistic material becomes cosmologically coupled to the expansion rate" in the recent dark-energy black-hole paper?
The recent paper "Observational Evidence for Cosmological Coupling of Black Holes and its Implications for an Astrophysical Source of Dark Energy" has made a splash in the popular press. ...
- 48.4k
3
votes
1
answer
39
views
Does rate of expansion of the universe affect perceived strength of gravitational pull?
As I understand expansion of the universe could be viewed as a constant negative pressure. So when we are looking at two bodies like Earth and Sun, from their perspective there should be a force ...
- 133
4
votes
1
answer
270
views
How can black holes possibly drive accelerating expansion of the universe?
(Potentially too broad, but all my questions are related to the paper in question.)
Recently there was an article published in Astrophysical Journal Letters that claims black holes "contribute ...
- 21.4k
5
votes
1
answer
739
views
What does it mean for a black hole to be "filled" with vacuum energy?
I've read the recent news about non-Kerr black holes coupling to the universe's expansion rate, and it looks like an excellent fit to the data. From the paper, I understand that these black holes grow ...
- 278
0
votes
2
answers
98
views
Mass matter, energy and "massless matter"
This is perhaps a rather silly question, or rather a matter of convention, but I would like to hear arguments about the appropriateness of certain definitions.
Traditionally, in chemistry and in pre-...
- 1,640