Tagged Questions
2
votes
0answers
48 views
de Sitter versus Minkowski QFT and cosmological constant
WMAP/Planck results confirm than we live in a de Sitter-like phase, i.e., a Universe with positive acceleration or positive cosmological constant! Therefore, I believe that a way to solve the ...
2
votes
0answers
74 views
Vacuum to vacuum transition amplitude
I have two questions about Vacuum to vacuum transition amplitude.
Can any particle stay in $|0\rangle$?
I was studying this topic from Srednicki's QFT book. He writes in eq.$(6.22)$
$$\langle0|0 ...
1
vote
1answer
85 views
Multiple vacua vs. vev's in qft
Take a (possibly supersymmetric) relativistic quantum field theory:
when we construct it, we suppose that there is a unique vacuum state $|0\rangle$ which is Lorentz invariant, vector of some Hilbert ...
1
vote
2answers
183 views
What is the expectation value of the number operator when the vacuum has a VEV?
The number operator N applied to a field whose vacuum has zero VEV gives $N|0>=0$. What if we apply it to the Higgs field?
The background of this question is that in popular scientific accounts, ...
3
votes
2answers
317 views
Creation of particle anti-particle pairs
I was reading some QFT notes and there is one point that I don't understand, they are justifying why we need QFT saying that the number of particles is not preserved once we consider special ...
5
votes
3answers
448 views
What really goes on in a vacuum?
I've been told that a vacuum isn't actually empty space, rather that it consists of antiparticle pairs spontaneously materialising then quickly annihilating, which leads me to a few questions.
...
2
votes
2answers
311 views
Why $\lambda\phi^4$ theory, where $\lambda>0$, is not bounded from below?
Why the following interaction, in QFT, $$\displaystyle{\cal L}_{\rm int} ~=~\frac{\lambda}{4!}\phi^4$$ where $\lambda$ is positive, represents a theory that is unstable (or unbounded from below as it ...
10
votes
4answers
546 views
Is there an intuitive description of vacuum entanglement?
People often refer to the fact that the vacuum is an entangled state (It's even described as a maximally entangled state).
I was trying to get a feeling for what that really means. The problem is ...
6
votes
1answer
857 views
Measured Higgs mass and vacuum stability
There is such a thing, called "stability bound" on mass of the Higgs boson.
The basic idea (as I understand it) is that we take Higgs self-coupling, and calculate its renormalization running. And it ...
2
votes
2answers
87 views
Is there any correlation between the energy density fluctuations of two separate systems in a vacuum state?
I think the title says it all. What I am curious to find out is if there are any observable changes in the fluctuations of zero-point energy in a vacuum state system that are the consequence of ...
4
votes
1answer
213 views
Does the vacuum energy problem of quantum field theory only occur in the Hamiltonian approach, or also in the path integral approach and in AQFT?
In a standard QFT class, you're being indoctrinated that there is the "infinite vacuum energy density problem".
(This is sometimes paraphrased as the "cosmological constant problem", which is in my ...
6
votes
3answers
726 views
What are the calculations for Vacuum Energy?
In wiki the Vacuum Energy in a cubic meter of free space ranges from $10^{-9}$ from the cosmological constant to $10^{113}$ due to calculations in Quantum Electrodynamics (QED) and Stochastic ...
3
votes
0answers
125 views
Stability of the vacuum state of interacting quantum fields
"Stability" is generally taken to be the justification for requiring that the spectrum of the Hamiltonian should be bounded below. The spectrum of the Hamiltonian is not bounded below for thermal ...
5
votes
1answer
216 views
Defining the ground state energy of a QFT
I would like to hear of some general discussion on how is the ground state and its energy defined in QFT and how does one go about finding it. (..at least in some simple cases I have seen the use of ...
10
votes
1answer
796 views
How to interpret vacuum instability of Higgs potential
If the Higgs mass is in a certain range, the quartic self-coupling of the Higgs field becomes negative after renormalization group flow to a high energy scale, signalling an instability of the vacuum ...
3
votes
2answers
565 views
Who first realized the uncertainty principle allows for virtual particle pair production?
For all I've read about Quantum Field Theory I've never seen the concept of the living vacuum accredited to someone in particular. Given the importance of this very application of the uncertainty ...
0
votes
0answers
254 views
Gravitation and the QFT vacuum
I'm asking this to get yet another lessson in the inability of QFT and GR to cohabit. Many people believe GR must yield to quantization. The question here is as to why the activity of the vacuum ...
3
votes
1answer
219 views
The vacuum as trigger
Do the apperance in the atomic nucleus of virtual matter-antimatter particle pairs play a role in the random nature of radioactive decay?
-1
votes
1answer
359 views
The difference between free energy and perpetual motion [closed]
What is the difference between free energy (over unity) and perpetual motion?
Please provide some examples, both real world and theoretical.
6
votes
2answers
718 views
Wheeler-Feynman theory, QED without fields, vacuum polarization
Initially Wheeler and Feynman postulated that, the electromagnetic field is just a set of bookkeeping variables required in a Hamiltonian description. This is very neat because makes the point of ...
