Questions tagged [color-charge]

The charge of the strong nuclear force is called "color".

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How much color charge does a quark carry? [duplicate]

If we look at QED, we can say that an electron carries the charge $$Q_\text{electr.}=-e = -1.602\cdot 10^{-19}\text{ C}$$ so how can we extend this to quarks? Would, for instance, $$ Q_\text{red} = ...
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Why use $SU(3)$ and not $SL(3, \mathbb{R})$ for color charge? [duplicate]

Why do we use the group $SU(3)$ and not $SL(3, \mathbb{R})$ for color charge? As far as I can tell, the $SL(3, \mathbb{R})$ is volume and orientation preserving, by the fact that it has unit ...
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Why don't green and anti-green gluons immediately annihilate each other?

I can't believe I haven't found an answer elsewhere..... I have read repeatedly about blue/anti-blue gluons, etc., but no reason as to why they don't destroy each other immediately..... Or maybe ...
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Color symmetries in variant QCD

Suppose we only have two colors, for example, red (R) and blue (B) to construct the wave functions of baryons and mesons and that the color symmetry is SU (2) and not SU (3). In this situation, ...
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Would Color Confinement apply in higher dimensions?

As I understand it color confinement comes from the fact that as the distance between two color charges increases the color potential energy increases, instead of decreasing, and the energy needed to ...
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What is the systematic way to determine the spin of lowest-lying states of baryons like $uuu$, $ssd$, $uds$ etc?

I learned that for the lowest lying states, $uuu$, $sss$, $ddd$ can only have $J=\frac{3}{2}$ $uus$, $ddu$, $ddu$, $ssu$ etc can only have $J=\frac{1}{2},\frac{3}{2}$ $uds$ can have $J=\frac{1}{2}, \...
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Is there a physical difference between the colors of quarks?

Is there any physical difference to the way, say, red quarks behave compared to green or blue ones? Or is it just an intrinsic property that they have that doesn't provide any physical difference ...
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Why do quarks and gluons have colour?

I asked a question here a few days ago and got some fantastic answers so I'm going to continue. Let me preface this by saying I know quarks do not actually have 'colour', but colour is some sort of ...
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A fundamental question about charge and speed of a particle [duplicate]

Hi everybody and happy 2019. In my teaching sessions sometimes someone asks questions i cannot truly answer (although i have many arguments on it) and here's one that really puzzles me: A massless (...
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How many antiquarks can be squeezed inside a nucleon without upsetting exclusion principle?

I read about a nucleon with 3 Strange quarks which clearly violates PEP, however this was soon resolved by introducing colour charges. Then I read about colour confinement where surplus energy can be ...
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What should I read to understand this question?

I understand the strong force as a Yang-Mills theory with $SU(3)$ color invariance. I understand that the quarks live in the fundamental representation of $SU(3)$ and that gluons live in the adjoint. ...
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Where do the color indices come back in $SU(3)$ Yang-Mills Quantization?

Can the partition function of $SU(3)$ (the Generic Partition function for a yang-mills theory found on the linked wiki page below), be split into a sum of 8 functional integrals for each gauge field? ...
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How do we show that gluon-fields have color?

I understand how to derive the QCD lagrangian based on certain assumptions about Quark fields and $SU(3)$ gauge invariance and in the final expression one finds the term $(A_µ)^c*T_c$ where $T_c$ is ...
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Coefficients of Color Potential in Quarks [duplicate]

I was wondering if there was a relation between the fractional coefficients $$2/3, 1/3$$ obtained when calculating color potential for quarks and the value of electric charge for the up and down quark....
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Is there something similar to time step increments for simulating a system of multiple particles in quantum mechanics?

In Newtonian Physics it is possible to simulate a system of multiple electrically charged bodies, that all exert an electric force on each other, using time step increments. For instance given the ...
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Do color changing interactions between up and down quark exist?

In our Standard Model course we wrote down the term for the quark-gluon interaction of the left handed $SU(2)_L$ quark doublet $q_L$ as: $\mathscr{L} = … + \bar{q}_L \gamma^\mu iG^a_\mu(x) \lambda^a ...
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Difference between boundedness (electrons around nuclei) and color confinement (quarks)

I have read these questions: How does the orbiting of electrons around nuclei START? Bound electrons don't move, right? Do different orbitals overlap in multielectron atom? What is the ...
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Colors sensitivity by human eye and light wavelength [duplicate]

I do not understand why human eye sees different colours from the LED TV/screen. Especially violet. For example, how we get yellow color on TV. There are 3 small diodes Red, Green Blue in LED screen ...
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What keeps quarks separate (strong force pulls, but what repels to equal out)

We know that the strong force keeps quarks together, that is mediated by gluons (and their charge is called color charge). We know that the residual strong force keeps neutrons and protons together in ...
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From Reflection Spectrum to Preceived Color

I have a reflection curve over the visible spectrum (350nm to 700nm) of a sample. Now, I am interested to know what preceived color one would see ? Is it possible to go from the reflection spectrum ...
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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) ...
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Can the three quark colors be considered to correspond to different particles?

Is it harmless to count three, say, up quark particles instead of one up quark with three colors, as well as 8 different gluons instead of one with different color?
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Quark-Gluon color relationship in pure QCD

Consider pure QCD, flavor turned off. There are 3 quarks and 3 anti-quarks given by the fundamental IRR of SU(3) and its conjugate rep. We associate the three colors and anti-colors with the three ...
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The “Big Rip” -vs- Color confinement [closed]

One model for the end of the Universe says that space will continue to expand faster and faster, until even atoms are ripped apart in the so called big Rip. It is also stated by QCD (quantum ...
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Understanding mathematical explanation for Chudakov Effect

I'm trying to better understand some properties of QCD and currently I'm looking into understanding color coherence. I've got the book "Elementary Particle Physics: Foundations of the Standard Model, ...
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How would an interaction with a single charge, and a charged weightless carrying particle behave?

We learnt about, among the other three fundamental interactions, the strong interaction. The particles that are affected by it are those with color-charge. It's carrying particles, gluons, have a ...
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Is it possible different coloured quarks have slightly different masses?

For example, could the red-down-quark have a slightly different mass to the red-up-quark? Since quarks rest masses are so much lighter than the particles they make up, that little bit of different ...
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Why does the $\Lambda^0$ exist?

In looking at the particle charts I see 3 Sigma baryons with very similar masses and other similar properties, which makes sense since they all have one strange quark plus two others from the (up,down)...
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$SU(3)$ Color Symmetry

I have following (maybe a bit general) question about the $SU(3)$-symmetry of color by quarks: If I consider the analogy to the $SU(2)$-symmetry of isospin $I$ crucially it concers the conservation ...
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Quark jet color

When a 2-jet event occurs due to a quark + antiquark emerging back-to-back, the jets ultimately decay to stable particles. Each jet starts with a quark (or antiquark) carrying a color and ends as a ...
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How to determine Gauge Boson charge?

Given the field strength: $$F^a_{\mu\nu} = \partial_\mu A^a_\nu - \partial_\nu A^a_\mu + g \; f^{abc} A^b_\mu A^c_\nu$$ We'd get interactions between three and four bosons, former one will look like:...
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Could we draw field lines for colour charge?

Electromagnetic charge can be represented with field lines. These are pleasingly intuitive and can be used to visualise Gauss's Law and Maxwell's Laws. Later on Gauss and Maxwell get rolled into a ...
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Quark colour charge at gluon emission/absorption

Suppose I have a very simple QCD diagram, where a quark emits a gluon and continues on. Can I describe such process through "usual" quantum mechanics? More specifically, can I use the concept of ...
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In nonabelian gauge theory, does the ordinary or covariant derivative go into the statement of current conservation?

Before equation (77.35), Srednicki's QFT book says We define the chiral gauge current $j^{a\mu}$ [where $a$ is a color index]. Its covariant divergence (which should be zero, according to Noether's ...
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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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What exactly is the color charge in QCD? [duplicate]

I don't have strong background in particle physics. Though, I had learnt a little of it. I have gone through the basic of these stuffs (pretty OK). If I have done my homework right, color charge (R,G,...
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What is the effect of the Gell-Mann matrices on color antiparticles?

I'm studying QCD and I can't understand how exactly are defined the color antiparticles. Indeed, we have the particle color triplet $(r,g,b)$. With the usual SU(3) algebra, we define the 8 Gell-Mann ...
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Color confinement and integer electric charge?

Quarks have electric charges proportional to one third of the elementary electric charge, but both mesons and baryons have integer electric charge. Is there some deep explanation from a more ...
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Why are 3 colors used in QCD?

The mapping of strong charge to RGB left me believing that there are only 3 conserved quantities in QCD. I recently came to the understanding that there are in fact 8 conserved quantities, as ...
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What's the difference between Quark Colors and Quark Flavours?

Each of the six "flavors" of quarks can have three different "colors". The quark forces are attractive only in "colorless" combinations of three quarks (baryons), quark-antiquark pairs (mesons) and ...
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$SU(3)$ global gauge group

Referring to the quantum observables of quarks, is it true that the color $SU(3)$ unitary representation commutes with all observables? I am not referring here to the local $SU(3)$ gauge theory, I ...
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How many kinds of “weak charges” exist?

For electricity, we have one charge, for the strong force three. How many are there connected to the weak force? Three, because of the W- and Z-particles? For the weak force, there is the isospin, ...
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How does quark color affect the identity of a hadron?

I've read about colors relating to quarks and hadrons and I know that they can change colors because of the exchange with gluons, but does changing color change the type of hadron? Does a proton ...
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Why does confinement apply only to quarks, and not to nucleons?

When energy is input in an attempt to break quark bonds one simply generates more quarks through hadronisation. The explanation my physics book gives for this is that "the strength of the strong ...
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Is there a colour “magnetic” field?

Does the colour charge of quarks brings a "colour magnetic field" into existence? When the quark is moving you should expect that it results in the same kind of magnetic field as a moving electric ...
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Can quarks have anti-colors? [closed]

What is the reason that the color properties we call red, green and blue have become tied to quarks, while what we call anti-red, anti-green and anti-blue has become tied to anti-quarks? Do note that ...
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Up/Down Quark Color and Isospin

I'm reading some notes that say the reason that the strong interaction conserve isospin is because the up and down quarks have the same color... but I'm not very convinced. Is this a universal truth? ...
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How many glueballs are there?

As I understand there are eight types of gluons (linear combinations of color/anticolor pairs with varying amplitudes) which can combine (for very short periods) to form glueballs. If there were no ...
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A few questions on quarks, gluons and the strong force

I wanted to answer for myself some pretty fundamental questions pertaining to the strong interaction, color charge and quarks, but I'm sort of stumbling on a few. So I wanted to find the reason/...
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Do quark charges repel one another?

Positive electrical charges repel other positive charges, and negatives repel negatives. But does that happen for quarks, too? I never saw mention of it, but if so, that would mean the up quarks in a ...