All Questions
Tagged with quantum-chromodynamics yang-mills
93
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Why is color confinement a difficult problem?
Assuming color force follows a constant rule of force instead of an inverse square rule of force. And that red, green and blue are all attracted to each other.
Why is color confinement considered a ...
user84158
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What is the relation between the Gribov problem and color confinement?
I have heard that the Gribov problem is in some way related to color confinement (For instance: Gribov copies and confinement). Although I understand what both the Gribov and confinement problems are, ...
- 17.8k
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1
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Isn't there a unique vacuum of the Yang-Mills quantum theory?
The theta vacua$^1$ of a Yang-Mills quantum theory are given by $$|\theta\rangle=\sum\limits_{n=-\infty}^{\infty}e^{in\theta}|n\rangle.$$ In Srednicki's Quantum Field Theory, he claims that the ...
- 26.8k
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Covariant Derivative in QCD: How does it act on gluons?
Let the covariant derivative be $$D_\mu = \partial_\mu + \text ig\ A_\mu^a t^a,\quad a=1,\ldots,8$$where $g$ is the bare QCD coupling, $A_\mu^a$ are the eight gluon fields and $t^a=\tfrac{1}{2}\lambda^...
- 2,648
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What is the Noether charge associated with the the color $SU(3)$ symmetry of QCD?
A version of the Noether's theorem applies to local gauge symmetries. What is the Noether's charge associated with a non-abelian gauge symmetry such as the color $SU(3)$ and how is that derived? I ...
- 26.8k
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2
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What are chromoelectric and chromomagnetic fields?
Are they the normal electric and magnetic fields from Maxwell fields? Or are they just the corresponding components from $G_{\mu\nu}^a$ (the gluon fields), say chromoelectric fields are simply $G_{0i}^...
- 3,691
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1
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What does that means? "QCD is a non-linear and non-trivial field theory?"
I know QCD is represented by the $SU(3)$ group and is non-abelian. Then, as a consequence QCD is a non-linear and non-trivial field theory.
I would like to know why? and what does that means?
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Which of the Wightman axioms are not incorporated by four dimensional quantum Yang-Mills?
I am trying to understand the quantum Yang-Mills existence problem but the best I have seen so far is the statement that there is no known interacting relativist field theory in four dimensions which ...
- 17.8k
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QCD Conjugate Variable Determination
This is not homework question. I have not been in school for over 40 years.
Are there conjugate variables in QCD? How are they determined?
I can relate to Heisenberg uncertainty in QM as the ...
19
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1
answer
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Inverse square rule for strong forces
Most of the forces induced by a point particle follows the $1/r^2$ rule. Then why does the strong force not obey it?
- 235
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What is relevant for Yang-Mills theory below $d = 4$?
There are two ways to write the Lagrangian for Yang-Mills, differing by the scaling of the Yang-Mills field. Fancy theorists tend to write
$$S = \int d^dx \, \frac{1}{4e^2} \, \text{tr}(F^2)$$
while ...
- 103k
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1
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"Color charge" of the adjoint fermion?
What kind of "color charge" does the adjoint fermion carry?
Let us consider the SU(N) gauge theory. The gauge field is in the adjoint representation (rep).
Well-Konwn: If the fermion is in SU(N) ...
- 4,336
3
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1
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745
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Is it the chiral anomaly which is solely responsible for having instanton effects (and therefore, the $\theta-$term) in the QCD action?
$\textbf{Fact 1}$ In principle, the QCD Lagrangian should contain a Lorentz invariant, gauge invariant, dimension-4 term $\sim\theta \text{Tr}[F^{\mu\nu}\tilde{F}_{\mu\nu}]$. This term, however, is ...
- 26.8k
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Axial anomaly in QCD VS axial anomaly in current algebra QCD
I would like to understand the distinction between an axial anomaly in QCD (Theta Vacuum: axion -> 2 gluons) and an axial anomaly in QCD of current (Chern–Simons term: pion->two photons, photon->three ...
- 215
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If the classical Maxwell theory describes E&M fairly, how well-done is the classical Yang-Mills theory for chromodynamics?
If the classical Maxwell theory describes electrodynamics (electromagnetism E&M) fairly well, how suitable would the classical Yang-Mills theory (say SU(3) color) describe the chromodynamics, and ...
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