All Questions
7
questions
3
votes
0
answers
47
views
Topology active subgroup for the QCD vacuum
I've been reading about the nontrivial topological structure of the QCD vacuum and, when studying the different equivalence classes created by the pure gauge fields, all papers say that it is possible ...
- 96
1
vote
2
answers
746
views
How does the underlying symmetry of QCD imply the allowance of a 4-gluon vertex?
Quantum chromodynamics allows for a four-gluon vertex such as this, in a diagram
Such a vertex would never be allowed in quantum electrodynamics, which has an underlying U(1) gauge symmetry.
I know ...
- 324
1
vote
0
answers
50
views
The remained global flavor symmetries of massless quarks after gauging electromagnetic $U(1)$
For $N_f$ numebr of massless quarks, we know that there are global symmetries
$$
\frac{SU(N_f)_L \times SU(N_f)_R \times U(1)_V}{Z_{N_f}}
$$
here $U(1)_V$ is the same as $U(1)$-Baryon number ...
- 4,336
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
1
vote
0
answers
195
views
Why does the $U(2n)$ flavor symmetry break down to a $U(1)$ group and an $SU(2n)$ group?
I am studying quantum field theory using Srednicki's textbook. Problem 83.1 is:
Suppose that the color group is $G_C=SO(3)$ rather than $SU(3)$, and that each quark flavor is represented by a Dirac ...
- 1,653
3
votes
1
answer
638
views
Problem with Bogoliubov transformations of an operator
I have a set of Bogoliubov transformation as follows:
\begin{equation}
a(\beta) = a \cos \theta (\beta) - \tilde{a}^\dagger \sin \theta (\beta)\\
\tilde{a}(\beta) = \tilde{a} \cos \theta (\beta) + a^\...
- 737
1
vote
0
answers
118
views
Uncharged Gluon Representation
I'm currently learning for an exam and in an old exam the question was posed:
If Gluons were uncharged, under which representation would they transform?
The ...
- 10.1k