Questions tagged [confinement]

Color confinement is the concept that particles that possess color charges (quarks and glouns) can not be found freely, and only color-free combinations can be observed.

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Is there any free and independent quark in nature? Or in products of collision between nucleons or atomic nucleuses in accelerators? Why is not it? [duplicate]

Quarks and leptons are only fundamental and essential particles which all matters were made from them. So like leptons, quarks must exist in nature or if all of them consumed in process of building ...
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Possible cases of matter fields for $SU(2)$ theory which retains asymptotic freedom?

Let us assume $4$ spacetime dimensions. QCD, the $SU(3)$ gauge theory with quarks as the matter fields, have the asymptotic freedom property as long as there are 16 quark flavors of mass below the ...
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Beyond sexaquarks?

There are some candidates for tetraquarks, pentaquarks or even now sexaquarks/hexaquarks. But, I wonder, what are the highest molecular quark states taking into account QCD? Are there heptaquarks, ...
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Is there a phenomenological Lagrangian which can reproduce the long-range potential between quarks?

The long-range potential between quarks in a confining gauge theory increases linearly with the potential: $$ V(r)=\sigma r \tag{1} $$ where $\sigma$ is the string tension. In QFT, one can calculate ...
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What does conservation of color charge mean for mixed states in QCD?

In quantum chromodynamics, in an interaction in which a quark and an anti-quark exchange a gluon, the color charge must be conserved. When we are talking about base states like $r\bar{b}$ it seems ...
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How are the constituent quark masses determined?

I was wondering how the constituent quark masses are determined (in wikipedia they claim $m_{u/d,const}\approx 350 $ MeV), but how is this in practise determined or estimated? I could not find any ...
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Is colour the conserved charge of global $SU(3)$ color symmetry?

Consider the Lagrangian consisting of three Dirac fields $$ \mathcal{L} = \sum_{a=1}^3 \bar{\psi}_a ( i \gamma^\mu \partial_\mu - m ) \psi_a$$ where $a$ is an internal index labelling the colour ...
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How do we known that $\langle \bar{\psi}_i \psi_j\rangle=(250 MeV)^3\delta_{ij}$?

I have started to read the phenomenology of QCD in low energy regime. I understand that, from the QCD renormalization group equation, the QCD becomes nonperturbative theory when energy scale is below $...
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Why do the nucleons interact via strong force even though they are color neutral?

Particles that transform non-trivially under color $SU(3)$ interact via strong nuclear force. However, neutrons and protons, despite being color singlets, interact via the strong force. How do we ...
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Why are gluons massless as their range is finite?

The range of electromagnetic waves and gravitational force is infinity and the particles exchanged during these interactions are photons and gravitons respectively. Both are massless following the ...
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How to understand confinement of 2+1d $U(1)$ gauge theory from instanton effects?

In Section 6.3.2 of XG Wen's book Theory of Quantum Many-body System, the confinement of $2 + 1 d$ compact $U \left( 1 \right)$ gauge theory was explained by the instanton effect. I want to know how ...
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How do scientists attempt to break quark confinement?

From what I understand, when energy is supplied to quarks, it elongates the gluon tube and when enough energy is put in, new quarks are formed, keeping quark confinement. However, I am inquisitive ...
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Can black holes have colour charge? [duplicate]

Does the no hair's theorem take into account all the elementary particles and forces, and in particular can a black hole have color charge?
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Do Neutron stars have free quarks?

Do Neutron stars have free quarks? Also Can Quark Stars be formed also due to this reason? Because of Asymptotic freedom high energy causes quarks to be free but according to the mass-energy ...
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It is said that the dual Meissner effect can explain confinement, but where is the Higgs?

It is said that the dual Misner effect can explain confinement. This refers to when the monopole field acquires a v.e.v.. The t'Hooft-Polyakov monopole arises in a theory with a Higgs. So how does the ...
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Is ${\cal N}=4$ Supersymmetric Yang-Mills in $D=4$ confining?

Is ${\cal N}=4$ Supersymmetric Yang-Mills in $D=4$ confining? Any intuitive reason why or why not?
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How does AdS/CFT help us understand non-perturbative aspects of QCD?

I've heard AdS/CFT has found applications in many areas of physics where nonperturbative aspects leave us crippled in making any simple calculations. Among these applications, I also have heard that ...
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Can free quarks exist?

I know that currently free quarks do not exist but can they exist under any circumstance? The Physicsworld article Quarks break free at two trillion degrees states that they do but I want a ...
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Are glueballs confined without a connection to quarks?

Without being bound to quarks through the strong force, is there any reason why glue balls would be confined? Are they confined
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Can we detect and measure color charge?

I was listening to the "Why This Universe" podcast about dark matter and Dr. Dan Hooper mentioned briefly that electric and color charge can be readily detected. Can color charge be ...
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Color confinement vs. Weak charge confinement

Sometimes, color confinement is explained loosely by stating that the gauge group of QCD, namely SU(3), is non-abelian gauge group and, therefore, tends to form narrow "flux tubes" through ...
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With enough fermions, does QCD confinement disappear?

It's been a while since I thought about QFT, but the following thing was puzzling me. I've often read that theories with a beta function that is asymptotically free at lowest order will likely suffer ...
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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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Quantum chromodynamics - why are there no $rrb$ or $ggr$ terms?

$$\Psi_{colour}^{qqq} = \frac{1}{\sqrt{6}}(rgb + gbr + brg -grb - rbg - bgr)$$ My lecturer stated that there cannot be any $rrb$ or $ggr$ terms in the expression above. I would like to understand what ...
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Area and perimeter

Apparently (?), a line operator over a very large loop with length $L$ can obey either perimeter law or area law, $-\log\langle U\rangle\sim L^a$ with $a=1,2$, respectively. We call these options &...
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In the history of the development of the standard model was there a version in which quark-antiquark pairs or flux tubes were the fundamental particle [closed]

Based on the observations of color confinement and no free quarks, I'm wondering if instead of a having quarks as fundamental particles, during development of the Standard Model was there ever a ...
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Do Quarks Exist?

Do Quarks Really Exist? Is there any experiment which can confirm the existence of Quarks and what kind of force is that which binds them to form neutron and proton?
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What would happen to a quark if it could be isolated, into what particles it would change? [closed]

WP defines as quantum charge the $-\frac{1}{3} e$ charge value of the down quark and as elementary charge the -1e of the electron. The elementary quark particle cannot be isolated in the lab and its ...
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Local order parameter for confinement in gauge theories

I would like some help clarifying what Zinn Justin is saying in his book "Quantum Field Theory and Critical Phenomena" p.805 on detecting confinement of gauge theories. In particular, I ...
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What is the current status (October 2021) of the Yang-Mills existence and mass gap problem?

One of the famous "millennium prize problems" is the "Yang–Mills existence and mass gap" problem, which in its official description by E. Witten and A. Jaffe has the following form:...
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What makes the (non-abelian) strong interaction so special that it leads to confinement?

The strong interaction has a coupling constant of $\alpha_s(91GeV)\approx 0.1$ whereas the weak interaction has a much lower coupling constant $\alpha_w \approx 10^{-6}$. Both theories are non-abelian ...
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What is confinement?

I just got confused about the meaning of confinement in QFT. The naive definition is that in QCD one cannot observe isolated quarks and gluons. This is a trivial statement because in any gauge theory ...
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Is a 6-quark particle viable?

It is my understanding (which may be flawed) that protons and neutrons are stable because the 3 (R, G, and B) quarks form a "white" color singlet. Wouldn't 6 quarks or even 9 quarks create ...
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Is it possible for an isolated quark to exist if it's bound to one or more non-virtual gluons to render the system color neutral?

We know color-neutral bound systems of quarks exist in the form of hadrons, we suspect color-neutral bound systems of gluons exist in the form of glueballs, we have a candidate particle which may be ...
Adam Lincoln Steele's user avatar
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What units is strong nuclear charge measured in? [duplicate]

Do particles have a strong nuclear charge in the same way as they have electric charge? If so what unit would be used to measure this? Would it be measured in Coulomb for instance?
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Primordial color charge fluctuations that failed to die out due to cosmic inflation

We know that ripping the quarks in a hadron apart will not give us free quarks, but rather new (anti-)quarks are generated that neutralize the color charges of the quarks. We also know that the total ...
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Why aren't all quarks clumped together in one giant hadron?

As far as I am aware, the strong interaction is attractive only, and its carrier, the gluon, is massless meaning it has unlimited range. If this is the case, how come we only observe quarks in pairs ...
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What happens to the individual quark(s) produced in a $W$ boson decay 'chain'?

Just over two-thirds of the time, a $W$ boson decays into quarks, usually an up quark and a down antiquark... Right? Since quarks hate being alone, what happens next? Does the up quark pull a single ...
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In the deconfinement phase, there are absolutely no interactions between the particles?

The Wikipedia article on Deconfinement says: "In physics, deconfinement (in contrast to confinement) is a phase of matter in which certain particles are allowed to exist as free excitations, ...
Arman Armenpress's user avatar
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What would happen to a lone quark?

If a quark simply popped into existence, what would happen to it? Or is this question unanswerable for some reason (e.g "a quark, by definition, exists with other quarks, and has no mathematical ...
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Do hadrons have color moments?

Hadrons have electrical moments since they are made up of both positive and negative charges. Water molecules have dipole moments for the same reason even though they are electrically neutral. Since ...
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Why are there no composite particles with fractional charges?

Mesons are composed of a quark and an anti-quark, so no fractional charge is possible mathematically. Baryons are composed of three quarks, no anti-quarks mixed in with quarks, so no fractional charge ...
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About the validity of the dilute gas approximation

In the compact QED (cQED) in $(2 + 1)$ dimensions confinement /deconfinement property is described in terms of boundness of monopole-antimonopole pairs (Berezinskii-Kosterlitz-Thouless phase ...
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Can mesons be in $b \overline{b}$, $r \overline{r}$, $g \overline{g}$ states?

Can a meson be in a pure $b \overline{b}$, $r \overline{r}$, $g \overline{g}$ state or does it have to be in the $\frac{1}{\sqrt{3}}\left(b \overline{b}+r \overline{r}+g \overline{g}\right)$ state? ...
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How can we split a proton? [closed]

I have heard the following statements: Quarks always exist in a group of 2 or 3, and can not stand alone. Protons are made up of 2 up quarks, and 1 down quark. Quantum mechanics allows us to entangle ...
Shaurya Sharma's user avatar
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How would quarks behave in the event of 'The Big Rip'?

I have always heard that you can't get a quark by itself because "the energy required to split them apart is enough to create another." But, in the case of The Big Rip, the idea is that ...
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How does the mere movement of gluons keep quarks together?

You know the strong force (the one that keeps quarks together). Well it works by exchanging gluons right? So how does that force keep the quarks together? I mean you can imagine that process as three ...
alienare 4422's user avatar
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What happens when one separates a quark-antiquark pair?

in particular, if the distance is more than about 1 fm?
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In a Big Rip scenario, would color confinement cause a singularity to form?

The energy in a gluon tube between quarks increases approximately linearly with the distance between them, and when that energy is sufficient to spawn a quark-antiquark pair out of the vacuum, it does ...
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QCD energy scale $\Lambda_{\rm MS} $, $\Lambda_{\rm QCD}$, ...?

Why there seems to be different conventions of QCD energy scales? Is that due to the running coupling? For example in Wikipedia https://en.wikipedia.org/wiki/Coupling_constant#QCD_scale: $$ \Lambda_{\...
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