All Questions
Tagged with quantum-field-theory cosmology
151
questions
3
votes
0
answers
139
views
Is it possible to treat fermion reheating from inflaton decay only perturbatively?
In case of an inflaton Lagrangian
$
\mathcal{L} = \frac{1}{2} (\partial_\mu \phi)^2 - \frac{1}{2}m_\phi^2 \phi^2 -h \overline{\psi} \phi \psi
$
where the inflaton field is coupled only to fermions ...
1
vote
3
answers
104
views
Vacuum energy density with respect to what reference frame?
Wikipedia quotes the observed vacuum energy density to be around $10^{-9}\frac{J}{m^3}$. Whatever the real energy density is, my question is, with respect to what reference frame is this being quoted?
- 13
5
votes
1
answer
186
views
Amplitude for neutron-proton conversion from first principles
I'm reading Dodelson's Modern Cosmology, and in one of the exercises on Big Bang nucleosynthesis it is quoted without reference that the amplitude for neutron-to-proton conversion is given by
$$|\...
- 349
2
votes
1
answer
705
views
Main idea behind this paper on Closed-time-path functional formalism
I tried to understand following paper: Closed-time-path functional formalism in curved spacetime: Application to cosmological back-reaction problems but I can't understand what is going on because I ...
- 3,043
5
votes
2
answers
301
views
Is the cosmological constant problem real? [duplicate]
The cosmological constant problem assumes that the cosmological constant (determined experimentally) can be identified with the vacuum energy density. Theroretical arguments from quantum gravity ...
- 191
4
votes
1
answer
333
views
What was above and below the QCD chiral symmetry breaking temperature?
Above a critical temperature in the Universe, there was probably a phase of unbroken approximate QCD chiral symmetry. Mathematically, the symmetry breaking is triggered when the operators $\bar{\psi}{\...
- 11.7k
2
votes
1
answer
158
views
The inflaton field exists in a superposition of energies. How does that affect the rate of cosmological expansion?
The inflaton field is a scalar field that each field value corresponds to different rates of expansion.
The field exists in a superposition of energies, that is, the wave function hasn’t collapsed. ...
- 455
0
votes
0
answers
193
views
Quantization of tensor perturbation
I have a problem when I am reading the paper "Probing the early universe with inflationary gravitational waves", written by Latham A. Boyle and Paul J. Steinhardt. Before I state my problem, I would ...
- 413
2
votes
0
answers
245
views
Temperature dependence of the Higgs VEV
Presumably, The Higgs field vacuum expectation value has a strong temperature dependence close to the electroweak symmetry breaking phase transition. Does this have known consequences for the ...
- 295
1
vote
0
answers
83
views
Cross-sections at zero temperature and high temperature for a process and its reverse
If the Feynman amplitude for a $2-2$ forward scattering $ab\to cd$ is denoted by $\mathcal{M}_{ab\to cd}$ and that of the reverse scattering process, $cd\to ab$, is denoted by $\mathcal{M}_{cd\to ab}$...
- 26.8k
1
vote
1
answer
122
views
Vacuum decay and Coleman-de Luccia bubbles
Can someone suggest me some good and detailed books (or notes) on the problem of vacuum decay and Coleman-de Luccia bubbles?
0
votes
0
answers
48
views
Quintessential models for dark energy
Following Sean Carroll here
There are good reasons to consider dynamical dark energy as an alternative to an honest cosmological constant. First, a dynamical energy density can be evolving slowly ...
0
votes
0
answers
96
views
How come the universe is considered flat if zero point energy is infinite?
If quantum field theory calculates that the vacuum energy is infinite and Einstein's theory of gravity implies this energy should produce a curvature of space-time then why shouldn't the universe be ...
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, ...
- 95.6k
1
vote
3
answers
561
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How inflation creates a universe from nothing?
I have a basic, mostly purely conceptual understanding of Quantum Field Theory, and after lots of Youtube (thanks PBS Spacetime!) I have an idea of how inflation works to turn the vacuum into a ...
- 749