Questions tagged [quantum-chromodynamics]
Quantum-ChromoDynamics (QCD) is the quantum field theory believed to describe the strong nuclear force.
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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}^...
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Chemical potential interpretation for QCD phase diagram
I'm studying the QDC phase diagram at finite densities and I'm having some trouble understanding the role of the chemical potential.
It's clear how, if I increase the density of particles at $T=0$, I ...
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QCD: In some phase diagrams, the axis are temperature and baryon chemical potential - what does it have to do with densities?
In this figure
one axis is the temperature (this one is no problem), the other one is the baryon chemical potential which causes my confusion.
Figure from here: Phase diagram of simplified QCD.
The ...
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Quark pair superconductor: Even parity is favorred than odd parity
It seems that the quark pair superconductor can be odd or even parity pairing respect to the parity $P$.
Say that the even parity has the form:
$$
\langle\psi C \gamma^5 \psi\rangle
$$
the odd ...
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Why there is only $t$-channel for $u+\bar d\rightarrow u+\bar d$ scattering?
I am reading Griffith's textbook on particle physics about the $u+\bar d\rightarrow u+\bar d$ scattering for QCD. On page 285, it says there is only one possible channel ($t$-channel):
Why there are ...
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How do I find the values for the structure constants ($f^{abc}$) of a gauge group?
How do I find the values for the structure constants ($f^{abc}$) of a gauge group, as a mean to find the tree-level amplitude for a process in which one of the tree-level diagrams is:
the process ...
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The divergence in QCD Series-- How many are they, and what do they mean?
I am referring to this question, and especially this answer.
In addition, QCD has - like all field theories - only an asymptotic
perturbation series, which means that the series itself will also
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How (or when) do gluons change the color of a quark?
I know a baryon is only stable when it contains a quark of each color. And as far as I know, the gluon essentially changes the color of a quark and moves onto the next, and this is what holds the ...
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How far can we separate two bound quarks?
If we try to separate two quarks bound into a meson or a hadron, the energy in the gluon field eventually will be large enough to spawn a quark-antiquark pair.
How far can we stretch that gluon ...
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What's the real resolution of the $U(1)_A$ problem?
To recap the problem, consider QCD with three massless quark flavors. There is a symmetry
$$SU(3)_L \times SU(3)_R \times U(1)_L \times U(1)_R$$
corresponding to independent rotations of the left-...
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Is forward scattering = no scattering?
What is forward scattering? If it is equivalent to no scattering, then why not call it "no scattering"?
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QCD and QED with unlimited computational power - how precise are they going to be?
My question is about quantum algorithms for QED (quantum electrodynamics) computations related to the fine structure constants. Such computations (as explained to me) amounts to computing Taylor-like ...
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Nambu-Goldstone bosons from a quantum anomaly symmetry breaking?
We know that:
Nambu-Goldstone bosons come from Goldstone theorem: a spontaneous (continuous)-symmetry breaking of the system leads to massless scalar modes.
quantum anomaly: is the anomalous ...
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Why are baryons equivalent to Skyrmions?
Baryons in quantum chromodynamics can be described as a bound state of three quarks. But they can also be described as a topological soliton of the pion field. How can both descriptions be equivalent?
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Could the universe have non-vanishing net colour charge?
I've heard that the strong force doesn't decrease in strength with increasing distance, and that's why quarks must be confined within hadrons. But could there be, say, a single quark out there, so ...
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