Trace of 4 Gell-Mann matrices

Does any one know what would be tr(tatbtctd), where ta etc are Gell-Mann matrices? This came about when analyzing the color factor for the compton effect for QCD. So, must be pretty common, but I could not find a proper reference. In general is there any reference for trace of arbitrary number of Gell Mann … Read more

Is color charge quantized?

I was reading this stackexchange question, and found the answer to my question not totally answered. Clearly there is color and anti-color in analogy to electric charge, and color charge clearly cannot vary from color to anti-color. However can color (or anti-color) continuously vary between a red green and blue basis, or is it like … Read more

What is anti-screening?

In his book “The Lightness of Being” Frank Wilczek (page 48) writes about screening and anti-screening. In screening, a bare charge attracts virtual particles of opposite charge which lessen the effect of the bare charge. He writes that anti-screening is the “opposite of screening” with no further physical explanation. This is an attempt to explain … Read more

Confirming an inconsistency of the Balitsky-Kovchegov equation between references

I’m comparing the form of the Balitsky-Kovchegov equation, which describes the splitting of low-momentum gluons, between different references, and I’m finding an inconsistency: most sources (1, 2, 3, 4, 5, etc.) give the relevant part of the equation as αsNc2π2∬ where the coordinates are related to each other by \begin{align} \vec{r} &= \vec{x} – \vec{y} … Read more

Is there something like Hawking radiation that makes protons emit component quarks?

If Hawking radiation can escape from black holes, could quarks perhaps become separated from protons despite it being “impossible” for that to happen? Answer Such a process is forbidden by energy conservation: the proton is the lightest baryon (that is the lightest bound state of three quarks). hawking radiation finds it’s energy by reducing the … Read more

Why are the ‘color-neutral’ gluons confined?

What makes the two ‘color-neutral’ gluons (rˉr−bˉb)/√2 and (rˉr+bˉb−2gˉg)/√6 different from the pure rˉr+bˉb+gˉg ? Why don’t they result in long range (photon-like) interactions? Answer There is no fundamental difference between the gluons (rˉr−bˉb)/√2 and (rˉb+bˉr)/√2. The first one is represented by the matrix Z=1√2(1000−10000) and the second by the matrix X=1√2(010100000). However, these two … Read more

Measuring strong coupling constant

How can the strong coupling constant be measured? Answer Through literally hundreds of experiments of dozens of process types, involving the strong interactions, and coordinated comparisons of precision measurements with detailed calculations of Quantum Chromodynamics (QCD). In the last 40 years, dozens of ingenious handles for precision determinations have been devised and compared, cf AttributionSource … Read more

When/ how were/are quarks formed?

We know that all particles can eventually be converted into energy. We know also that electrons were and still are formed by pair production from a 1MeV photon. Do physicists have yet any idea how quarks were formed? When did that happen, before BB? Can they be produced at any time in the present? In … Read more

Does the number of left handed chiral quark superfields always equal half the number of quark flavours?

In Weinberg’s “The Quantum Theory of Fields Vol III” page 267 we’re told that nf=2Nf. Where nf are the number of flavours and Nf is the number of left chiral quark superfields (or the number of corresponding left chiral anti-quark superfields). This implies that the number of left chiral quark superfields is half the number … Read more

Why scattering of red and blue quark only involves Gμ8G_8^\mu?

According to the author C. G. Tully (Particle physics in a nutshell), the scattering of a red and blue quark only involves Gμ8. How come this is so? I thought Gμ3 and G8 only mediate between quarks of the same color? If we consider the following term which comes from the interaction term of QCD: … Read more