All Questions
26
questions
4
votes
1
answer
209
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 $$ds^2=-dt^2+b^2(t)d\vec x^2.$$
...
- 503
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
74
views
Exact solution to the Mukhanov-Sasaki equation for a massless scalar field
I am reading some cosmology review papers and I am at the section in which the equation of motion for a massless scalar field in a de Sitter spacetime is derived. The equation of motion for the ...
- 11
1
vote
2
answers
152
views
Whether vacuum energy gravitate?
What is the relationship between vacuum energy and gravity, particularly in terms of gravitational effects and its contribution to the overall cosmological constant? Does vacuum energy possess ...
2
votes
1
answer
137
views
Second Law of Thermodynamics and Particle Creation/Annihilation
I have a question regarding the second law of thermodynamics:
In most proofs of the second law of thermodynamics (like Jaynes' proof) the phase space is considered to be of constant dimension.
However ...
- 1,488
7
votes
0
answers
132
views
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
2
votes
1
answer
173
views
Decay of the time derivative of solutions of the Klein-Gordon equation in decelerating expanding space-times
Suppose that we have a model of a universe* given by a flat FLRW metric.* In short, the model universe has $n\in\mathbb N$ dimensions, is homogeneous, isotropic and its expansion is governed solely by ...
2
votes
1
answer
704
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
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
1
vote
1
answer
121
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?
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, ...
- 95.5k
2
votes
0
answers
98
views
What's the difference, if any, between Soft Hair & Quantum Hair
In the early 90s, John Preskill, Sidney Coleman, Frank Wilzcek and Lawrence Krauss presented a series of papers [1][2][3] on Quantum Hair on Black Holes due to Cosmic strings in a number of ways ...
- 425
1
vote
1
answer
932
views
Can our universe be a true vacuum bubble?
The paper "Spontaneous creation of the universe from nothing" by Dongshan He, Dongfeng Gao and Qing-yu Cai
claims that our universe was created by the quantum fluctuations in the metastable false ...
- 29
3
votes
1
answer
95
views
Would the formulation of a theory of quantum gravity in the presence of a nonzero cosmological constant depend on the origin of the latter?
The cosmological constant is the coefficient of a term in the Einstein tensor for which there are no a priori reasons to assume it to be zero, so that it could be regarded as a fundamental constant of ...
- 9,304
1
vote
1
answer
125
views
Is quantum theory useful to describe the whole cosmos? [closed]
We often say that QFT describes the nature on a fundamental level. However this is indeed a very complicated theory for which the calculations related to the interaction of just a few particles simply ...
user56963