All Questions
Tagged with cosmology quantum-field-theory
56
questions with no upvoted or accepted answers
8
votes
0
answers
258
views
The emergence of space-time from entangled states
I recently read an article by Yasunori Nomura (https://arxiv.org/abs/1711.05263), in which he says that space-time is an emerging phenomenon. At the same time, space-time disappears when the ...
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8
votes
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answers
145
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Does the Standard Model plasma develop a spontaneous magnetisation at finite temperature?
Reference: arXiv:1204.3604v1 [hep-ph] Long-range magnetic fields in the ground state of the Standard Model plasma.
Alexey Boyarsky, Oleg Ruchayskiy, Mikhail Shaposhnikov.
The authors of this paper ...
- 16.6k
7
votes
0
answers
132
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Is GR the only theory in physics which cares about absolute energy?
In my QFT course, they justify dropping the vacuum energy as 'physics only cares about relative energies except for GR in the stress-energy tensor'.
Is this strictly true?
- 2,604
7
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438
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750 GeV diphoton resonance: KK graviton?
As everybody of you may know at LHC they found this probable resonance (https://cds.cern.ch/record/2114808, https://cds.cern.ch/record/2114853?ln=en). It may be a scalar or a KK graviton mode. Now, ...
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6
votes
1
answer
147
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Does Goldstone theorem have anything to do with Cosmic string
Cosmic strings are formed due to topological defects during symmetry breaking phase transition in early universe.
While Goldstone theorem states whenever we have continuous symmetry and it is ...
- 3,043
6
votes
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answers
150
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$f_{NL}$ non-Gaussianity in cosmology
In the context of cosmology, what is meant by "..arbitrary quadratic non-Gaussianity i.e non-Gaussianity that is described to leading order by a 3-point function.."? (.."quadratic non-Gaussianity" ...
- 4,561
5
votes
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answers
158
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Meaning of the simplest potential of quintessence models. Fields in denominator?
I am reading Sec. 1.12 of the Cosmology book by Weinberg.
In this section he explains the very simple model of quintessence which attempts to provide a dynamical explanation of the smallness of the ...
- 2,197
4
votes
1
answer
209
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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 $$ds^2=-dt^2+b^2(t)d\vec x^2.$$
...
- 503
4
votes
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answers
109
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What is the best way to describe a classical field in quantum field theory (coherent state)?
In quantum field theory, we have the following expansion on a scalar field (I follow the convention of Schwarz's book)
$$\phi(\vec{x},t)=\int d^3 p \frac{a_p exp(-ip_\mu x^\mu)+a_p^{\dagger}exp(ip_\mu ...
- 442
4
votes
0
answers
406
views
What is the current status or resolution of Greisen–Zatsepin–Kuzmin (GZK) cosmic-ray paradox?
The Greisen–Zatsepin–Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy.
A number of ...
- 4,336
4
votes
1
answer
662
views
Quantum fluctuations producing CMB fluctuations also cause inflation to be eternal?
It is believed that quantum fluctuations in the inflaton field caused inflation to end at different times in different places, which led to CMB fluctuations (1 part in 100,000).
Eternal inflation ...
- 855
4
votes
0
answers
182
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How to understand particle decoupling in the early universe?
We often say that when the rate of some interactions, say the beta decay and electron capture, are slower that the rate of universe's expansion, then the corresponding particles, say neutrinos, ...
- 3,691
4
votes
2
answers
509
views
What is the interpretation of a wave function of the Universe in Hawking's no boundary proposal?
In the path integral formalism we have an in state $\Psi_{in}[\phi]$ and and out state and we find the amplitude for going from one to the other:
$$\Delta[\Psi_{in},\Psi_{out}] = \int \Psi_{in}[\phi]...
user84158
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 ...
3
votes
0
answers
122
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Are trans-Planckian field values a problem for the relaxion?
The relaxion is a new model-building gadget that solves the hierarchy problem by allowing the Higgs mass term to dynamically relax to zero.
To describe it as simply as possible, leaving a lot out: we ...
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