Are Different Charged Gluons Repulsive in the Gluon-Gluon Four-Point Vertex?

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Discussion Overview

The discussion revolves around the nature of interactions between different charged gluons in Quantum Chromodynamics (QCD), specifically focusing on the four-point vertex and whether the first component of the interaction is repulsive. The scope includes theoretical considerations and interpretations of Feynman diagrams.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether two different charged gluons interacting at the four-point vertex are repulsive, referencing specific Feynman diagrams.
  • Another participant emphasizes that one cannot derive physical quantities from a single diagram and must consider all contributing diagrams together.
  • A participant expresses a belief that the first diagram may yield repulsive results for differently charged gluons, while suggesting that other diagrams might indicate attractive interactions.
  • Some participants challenge the meaningfulness of isolating one diagram for analysis, arguing that it does not provide a complete picture of the interaction.
  • There is acknowledgment of the participant's beginner status, with some responses indicating that their question may not be valid within the context of QCD.

Areas of Agreement / Disagreement

Participants generally disagree on the validity of isolating a single Feynman diagram to determine the nature of the interaction. While some express interest in the first component, others argue that it is not meaningful without considering all diagrams involved.

Contextual Notes

The discussion highlights limitations in understanding due to the complexity of QCD and the necessity of evaluating multiple diagrams for a comprehensive analysis. There is also a dependence on the definitions and interpretations of the diagrams in question.

simplemind
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Hello,

First,i am an absolute beginner in QCD.

As i have seen there are six different Feynmangraphs for the Four-Point vertex.
Swordfish,Box,...

I am interested in the first of the six where the two gluons met in a point and goes away.
My question now is.
If for this case two different charged Gluons interact are they repulsive?

I am reading

https://link.springer.com/article/10.1140/epjc/s10052-020-8260-8

and take a look on the picture on (5.14)

I am interested in the action of the first of the three posibilities the cross and not the lines.
 
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simplemind said:
i am an absolute beginner in CCD
I think you mean QCD.

simplemind said:
first of the six
There is no standard counting. "First" does not specify.

simplemind said:
If for this case

You can't get a physical quantity by calculating one diagram (it likely won't even be finite). You need to calculate the sum of all diagrams that contribute to a process.
 
Thanks but i only want to know if the first component acts repulsive or not.
From the sign it is different to the two negative others.
I think it is possible to anwer.
 
simplemind said:
i only want to know if the first component acts repulsive or not
And this is a meaningless question because, as @Vanadium 50 said, you have to look at all diagrams for a given process together; just looking at one tells you nothing. So it doesn't even make sense to ask if just one diagram "acts repulsive"; just one diagram by itself is physically meaningless.
 
Thanks but i am interested in it.Maybe it is meaningless in this case.
All diagrams are also interesting but as i said i am interested in the first component.
The background is that diagram 2 and 3 have a gluon between and diagram 1 not!
So i assume that the first diagram has repulsive results wenn the charge of the gluons is different.
For diagram 2 and 3 i think it is attracitve for different charged gluons (other sign as component 1 ) because there is a spin 1 gluon between.
Maybe i am completely wrong because i am a beginner.
I still think that it is possible to give an answer.
 
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simplemind said:
Maybe i am completely wrong because i am a beginner.
If you think you are asking a meaningful question that can be answered, yes, you are wrong.

simplemind said:
I still think that it is possible to give an answer.
Unfortunately it is not, for reasons that have already been explained.

Thread closed.
 

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