All Questions
25
questions
4
votes
1
answer
110
views
Is the amount of dark matter per galaxy the same as you look back through time (further away from earth)?
In the hope that it may inform us about the development/evolution (if any) of dark matter over time, are there any differences (eg. in structure or concentration) in the dark matter at large radial ...
- 351
1
vote
1
answer
77
views
"Penrose Functional Degrees of Freedom" ( PFDoF) as a source of dark mass
In his book "Fashion, Faith, and Fantasy in the New Physics of the Universe" Sir Roger Penrose mention ( referring to his older works and specially Penrose-Hawking Theorem) the possibility ...
- 2,063
3
votes
4
answers
2k
views
General Relativity "doesn't quite work" without dark matter?
I am taking an astrophysics course, and my astro professor said that "we need to introduce dark matter because Einstein's general relativity doesn't quite work without it".
I wanted to ...
- 303
1
vote
2
answers
143
views
The slowing of expansion in the matter dominated era
On all the graphs of the inflation of the universe, the era dominated by matter is slowing the rate of expansion. With an intuitive explanation (for all you science communicators out there) could you ...
0
votes
1
answer
1k
views
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
-1
votes
1
answer
137
views
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 ...
- 4,170
2
votes
0
answers
168
views
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 ...
- 7,592
0
votes
0
answers
35
views
Could quantum vacuum polarization increase GR frame dragging beyond the predicted values and therefore replace DM explanation of galactic rotation? [duplicate]
image source credits:David Butler
This anomalous speed rotation distribution of galaxies is today mainly contributed to Dark Matter.
However, since a definitive experimental measurement and ...
- 4,170
3
votes
2
answers
133
views
Is there an acknowledged unsolved problem in some cosmological theories with respect to "dark" matter and general relativity?
Some mainstream cosmological hypotheses hold both that:
general relativity is correct and universal; and
a form of "dark" matter exists that is, in somewhat of a misnomer, "non-...
- 153
0
votes
1
answer
122
views
Could Dark Matter imply the existence of Dark energy? [closed]
This is admittedly a simple example, but it seems to check out. Consider the standard metric for the Schwarzschild solution in coordinates $(t, r,\theta,\phi)$:
$$ g_{oo} = U, \ g_{11} = V, \ g_{22} = ...
15
votes
4
answers
3k
views
If dark matter can't lose kinetic energy, then why is it not traveling at relativistic speeds?
I have read this question:
The only way you can do this is to remove kinetic energy from the system.
With normal matter this is done through electromagnetic interactions, which turn the kinetic ...
- 29k
3
votes
1
answer
337
views
If dark matter can't clump together, then where was it when the observable universe was much smaller at the beginning of the universe?
I have read this question:
To zeroth order, dark matter can only 'clump' as much as its initial energy (obtained soon after the big-bang) allows. One example of such a 'clump' is a 'Dark Matter Halo' ...
- 29k
2
votes
1
answer
207
views
Can Integrating out Dark Matter give Modified Gravity?
I'm sure I misunderstood something obvious, but reading this question, I wondered what philosophically is the difference between modified gravity (like TeVeS, f(R), etc.) and dark matter, if/since we ...
- 232
0
votes
2
answers
118
views
Dark matter and velocity [duplicate]
We know that as the speed of an object increases, so does its relativistic mass.
But can it be said that dark matter may be due to the increasing relativistic mass of nebulae, stars, galaxies, etc. ...
9
votes
1
answer
124
views
Cosmological consequences of the mass-energy content of gravitational waves
This paper published in 1969 indicates that a majority of the mass-energy of the universe may be contained in gravitational waves:
"Turning next to phenomena on a galactic scale, we find it ...
- 24.8k