All Questions
Tagged with quantum-field-theory cosmology
25
questions
20
votes
3
answers
8k
views
Why do neutrino oscillations imply nonzero neutrino masses?
Neutrinos can pass from one family to another (that is, change in flavor) in a process known as neutrino oscillation. The oscillation between the different families occurs randomly, and the likelihood ...
- 1,516
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
15
votes
3
answers
2k
views
What are quantum fluctuations, really?
So, I have read a lot about quantum fluctuations, and how they are responsible for:
Lamb shift
Spontaneous emission of photons from excited atomic states
Casimir effect
...
and the explanation ...
- 24.9k
9
votes
1
answer
2k
views
Dirac Equation in General Relativity
Dirac equation for the massless fermions in curved spase time is $γ^ae^μ_aD_μΨ=0$, where $e^μ_a$ are the tetrads. I have to show that Dirac spinors obey the following equation:
$$(−D_μD^μ+\frac{1}{4}R)...
- 353
8
votes
3
answers
1k
views
Physical origin of the inflaton field?
I have two particular questions regarding the inflationary scenario. They are:
What is the physical origin of the inflaton field?
Why has the potential of the inflation field its particular form?
- 1,323
7
votes
5
answers
8k
views
Nothing vs. empty space
This question quotes Hawking saying:
[...] you enter a world where conjuring something out of nothing is possible (at least, for a short while). That's because at this scale particles, such as ...
- 676
4
votes
2
answers
5k
views
Is it possible that the Big Bang was caused by virtual particle creation?
As far as I understand, it is understood that throughout the universe there exists, what is known as, a quantum field from which, due to its fluctuations, temporary (pairs of) virtual particles ...
- 431
7
votes
1
answer
511
views
Does zero point energy really contribute to the cosmological constant?
The zero point energy is usually supposed to contribute to the cosmological constant. And the mismatch between the small cosmological constant compared with the huge zero point energy is deemed as one ...
- 4,452
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
3
votes
1
answer
362
views
What is the energy density of the inflaton field?
I am trying to compare the theoretically calculated vacuum energy density according to quantum field theory with the energy density of the inflaton field, in joules per cubic meter (or Pascal). I ...
- 65
-1
votes
1
answer
934
views
Universe from nothing? [duplicate]
I just finished the book of Lawrence Krauss "Universe from nothing" and he said that virtual particle can pop to existance from nothing by quantum fluctuations of the field from the vacuum and in the ...
12
votes
2
answers
2k
views
The difference between The Dilaton and The Radion?
I have read this question on the Dilaton, but I am a little confused with the distinction between the Dilaton and the Radion.
I definitely have the feeling that these two scalar fields are different ...
- 1,617
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
6
votes
1
answer
310
views
Would quantum fluctuations cause problems for scalar-field inflation?
Wheeler once said that spacetime would be highly curved at very small scales because of the uncertainty principle for energy-momentum. In which case the spacetime becomes very bumpy and not smooth ...
- 3,691
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