All Questions
18
questions
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 ...
- 619
2
votes
0
answers
75
views
Perturbative reheating
Are there any inflation models in which reheating would start perturbatively? I mean the non-perturbative process named as preheating (via parametric resonance) would be either inefficient or absent ...
- 3,691
4
votes
0
answers
409
views
What is the current status or resolution of Greisen–Zatsepin–Kuzmin (GZK) cosmic-ray paradox?
The Greisen–Zatsepin–Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy.
A number of ...
- 4,336
4
votes
2
answers
446
views
Can Higgs potential provide a cosmological constant?
Usually, in particle physics, people do not care about a constant term in scalar field potential. Rather, attentions are paid to the local profile at the minimum. But in the context of cosmology, the ...
- 3,691
1
vote
0
answers
85
views
To which particles does the inflaton field preferably couple?
I am studying the (p)reheating dynamics and I would like to know if it is a reasonable assumption to consider a generic inflaton field (not the Higgs-inflaton) to be coupled with the same intensity to ...
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
$$|\...
- 349
0
votes
0
answers
94
views
Vanishing integral in deriving stress-energy tensor from action
In the derivation of the energy-stress tensor for a scalar field (context: Inflation Theory for Cosmology) by varying the action with respect to the metric, the integral over spacetime that is ...
- 548
0
votes
1
answer
250
views
Physical understanding of the change in scattering cross-sections at finite temperatures
I am familiar with the computation of scattering cross-sections in zero temperature quantum field theory.
How does a scattering cross-section typically behave at temperature $T$?
Let the cross-...
- 26.8k
2
votes
1
answer
290
views
True/ false vacuum physical constants
Vacuum decay is the ultimate ecological catastrophe; in the new vacuum
there are new constants of nature; after vacuum decay, not only is
life as we know it impossible, so is chemistry as we know ...
- 23
1
vote
1
answer
141
views
Why is the coupling of the matter field with the inflaton field neglected at the inflationary epoch?
The simplest model of inflation involves a hypothetical, yet undiscovered, single scalar field $\phi$ called \emph{inflaton}. The action of this scalar field minimally coupled to gravity is given by $$...
- 26.8k
6
votes
1
answer
381
views
Difference between "C-violation without CP-violation" and "C-violation with CP -violation"
Consider two possible decay channels of a massive particle as $X\to A+B$ and $X\to C+D$ with decay rates $r$ and $1-r$ respectively. Let the decay rates of its antiparticle into channels $\bar X\to \...
- 26.8k
4
votes
5
answers
10k
views
Did quantum fluctuations create matter and energy out of nothing?
I found a popular science article explaining that the existence of the Higgs particle can be interpreted to mean that matter and energy are created by quantum fluctuations of nothingness (i.e. the ...
- 101
1
vote
1
answer
122
views
Temperature and particles and fields
When I studied Thermodynamics the way I learned things and the way I understood them is that temperature is a quantity that appears and is relevant just when studying macroscopic matter.
Indeed, all ...
- 36.4k
0
votes
2
answers
280
views
What would have been the story of the Universe if there was no mechanism to produce massive fundamental baryonic particles? [duplicate]
Thanks for those of you who took their time answering my problem but it seems that there is a misunderstanding between us. Most answers are based on the assumption of Electroweak symmetry breaking ...
- 1,290