All Questions
9
questions
1
vote
1
answer
77
views
Justifying the identification of eight gluons with the ${\bf 8}$ from ${\bf 3}\otimes{\bf 3}^*$
When we combine the fundamental ${\bf 3}$ and antifundamental ${\bf 3}^*$ of color $SU(3)$ of QCD i.e. single quark of three colors and a single antiquark of 3 anticolors, nine states are obtained. ...
- 11.8k
0
votes
1
answer
185
views
Is $SU(3)$ (and not $U(3)$) the symmetry group of color interactions because $U(1)$ is already used for EM?
I have already seen this question. It was answered that $U(3)$ can be decomposed into $SU(3) \times U(1)$, and $U(1)$ is already used for the EM interaction. Still, I wonder why the EM interaction ...
-1
votes
1
answer
324
views
Construct color octet
I'm reading about color octet, considering $r= \begin{bmatrix}1 \\ 0 \\ 0 \end{bmatrix}$ $b= \begin{bmatrix}0 \\ 1 \\ 0 \end{bmatrix}$ $g= \begin{bmatrix}0 \\ 0 \\ 1 \end{bmatrix}$ and $\lambda_{i}$ ...
- 49
1
vote
1
answer
690
views
Viable combinations of gluons interacting with colour singlet states
A proton-proton scattering event cannot take place with the exchange of a single gluon. The argument is that an attempt to draw a Feynman diagram for this process results in colourful outgoing states ...
- 3,569
3
votes
1
answer
270
views
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 ...
- 756
2
votes
1
answer
376
views
Why do we say that gluons carry color charge?
We know that gluons are Lie algebra $su(3)$-valued one-form fiels $A_{\mu}$. And because of $[A_\mu,A_\nu]$ does not vanish generally for the non-Abelian case, gluons have self-interactions. Now how ...
- 3,691
5
votes
1
answer
672
views
Group theoretical reason that Gluons carry color-charge and anti-colorcharge
I was wondering how it is possible to see from the $SU(3)$ Gauge Theory alone that Gluons carry two charges colors: $g\overline{b}$ etc.
Some background:
The W-Bosons (pre-symmetry breaking) form an ...
- 10.1k
6
votes
0
answers
239
views
From $U(3)$ to $SU(3)\times U(1)$ Color symmetry. There is a "gluon" photon-like?
Suppose that $U(3)$ was the gauge group. We can decompose this as
$U(3)=U(1)\times SU(3)$,
which implies that in addition to the $SU(3)$ that has eight generators corresponding to eight gluons, there ...
- 558
14
votes
2
answers
2k
views
Why $SU(3)$ and not $U(3)$?
Is there a good reason not to pick $U(3)$ as the colour group? Is there any experiment or intrinsic reason that would ruled out $U(3)$ as colour group instead?
- 558