All Questions
Tagged with quantum-field-theory cosmology
151
questions
2
votes
1
answer
329
views
Fokker-Planck equation from Langevin equation in stochastic inflation
I'm reading this paper by Starobinsky and Yokoyama where they give the coarse-grained equation of motion,
$$
\dot{\bar{\phi}}({\bf x},t ) = -\frac{1}{3H}V'(\bar{\phi}) + f({\bf x},t)
$$
where $f({\bf ...
CommunityBot
- 1
4
votes
1
answer
210
views
Is gravitational particle production due to symmetry breaking?
A well-known fact about QFTs in curved spacetimes is that there is a phenomenon of particle production in expanding universes, these being described by the line element $$ds^2=-dt^2+b^2(t)d\vec x^2.$$
...
CommunityBot
- 1
32
votes
4
answers
13k
views
Why is quantum gravity non-renormalizable?
The book The Ideas Of Particle Physics contains a brief treatment of quantum gravity, in which the claim is asserted that if one attempts to construct a model of gravity along the same lines as QED, ...
- 207k
2
votes
0
answers
44
views
Feynman rule from dynamical Chern-Simons
Consider the following action that
\begin{equation}
S = \int d^4x\sqrt{-g}\left(-\frac{1}{2}(\partial\phi)^2 + V(\phi) + \frac{2R}{\kappa^2}
- \frac{\phi}{4f}{}^*RR\right)
\end{equation}
where
\...
- 714
4
votes
1
answer
662
views
Quantum fluctuations producing CMB fluctuations also cause inflation to be eternal?
It is believed that quantum fluctuations in the inflaton field caused inflation to end at different times in different places, which led to CMB fluctuations (1 part in 100,000).
Eternal inflation ...
CommunityBot
- 1
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 ...
- 6,504
0
votes
1
answer
102
views
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 ...
- 12.7k
4
votes
2
answers
509
views
What is the interpretation of a wave function of the Universe in Hawking's no boundary proposal?
In the path integral formalism we have an in state $\Psi_{in}[\phi]$ and and out state and we find the amplitude for going from one to the other:
$$\Delta[\Psi_{in},\Psi_{out}] = \int \Psi_{in}[\phi]...
CommunityBot
- 1
1
vote
1
answer
827
views
How are Dark Energy and the Inflaton Field related?
My understanding of Inflation Theory:
Before $10^{-35}$ seconds the universe began to cool and the Inflaton Field approached a false vacuum. When it reached this false vacuum, there was a constant ...
6
votes
1
answer
1k
views
Virtual particle density in an expanding Universe
As the universe continues to accelerate in its expansion, does the virtual particle density decrease or remain the same throughout spacetime?
- 319
0
votes
0
answers
97
views
If dark energy has constant density, would it still be subject to quantum variations; would increase/decrease be symmetrical, or would one take over?
There are different suggestions, but it stills seems like the basic scenario is for dark energy to have constant density, as a property of space (and as represented by the cosmological constant in ...
- 15
1
vote
0
answers
828
views
Comoving and physical momentum in a Friedmann universe
It is most probably a very basic question, but I'm a bit stuck with it. Let us consider a spatially flat Friedmann universe with the usual metric
$$ds^2=dt^2-a^2(t)\left(dr^2+r^2d\vartheta^2+r^2\sin^...
2
votes
0
answers
24
views
Why is there an infinite supply of energy in slow-roll inflation?
The physical model of inflation includes a metastable false vacuum, or a slow-roll field on a flat potential. In either case, I just realized how this is completely insane. With the exponential growth ...
- 619
1
vote
3
answers
145
views
Why doesn't frozen-out dark matter annihilate later during structure formation?
The so-called freeze-out of dark matter is based on a homogeneous description. However, in the later stages of the universe, where structures form, it seems very likely that the reaction rate would ...
- 6,504
2
votes
2
answers
98
views
Why does the mechanism producing matter-antimatter asymmetry keep our universe electrically neutral? Any general argument?
I've noticed what seems to be a fine-tuning issue. To be more specific, electric neutrality implies that the amount of lepton asymmetry produced through some unknown processes precisely cancels out ...
- 589