How many Feynman diagrams do I draw?

In summary, the speaker is currently studying quantum field theory and is confused about the number of Feynman diagrams needed to compute the amplitude of various interaction terms. They mention that Tong presents Feynman diagrams through examples, such as nucleon-nucleon scattering where two diagrams are drawn with the labels for outgoing momentum flipped on one. However, for meson-meson scattering there is only one diagram. The speaker is unsure why a second diagram is not needed in this case, and is seeking further clarification on this topic.
  • #1
mjordan2nd
177
1
I'm currently going through the interaction part of Tong's lecture notes on quantum field theory, and I'm a bit confused about how many Feynman diagrams I need to draw in order to compute the amplitude of various interaction terms. Tong presents Feynman diagrams through a series of examples. For instance for nucleon-nucleon scattering Tong draws two diagrams, with the labels for the outgoing momentum flipped on one diagram with respect to the other. However for meson-meson scattering there is a single diagram. Why don't we need a second diagram in the meson-meson case with the labels of the outgoing momentum flipped on the second diagram? I don't understand how to see this without using Dyson's formula.
 
Physics news on Phys.org
  • #2
Two different mesons?
More context would help.
 
  • #3
The meson scattering I'm looking at is indeed [itex]\phi \phi \to \phi\phi.[/itex]
 

1. How do I determine the number of Feynman diagrams to draw for a particular process?

The number of Feynman diagrams that need to be drawn for a process is determined by the number of particles involved in the process. Each particle interaction corresponds to a vertex in the Feynman diagram, and the number of vertices determines the number of diagrams to be drawn.

2. Do I need to draw all possible Feynman diagrams for a given process?

No, it is not necessary to draw all possible diagrams for a process. Certain diagrams may be negligible due to their low contribution to the overall probability of the process. Experienced physicists can use their knowledge and intuition to select the most relevant diagrams to draw.

3. Can I use a computer program to generate Feynman diagrams?

Yes, there are several computer programs available that can generate Feynman diagrams for a given process. These programs use algorithms and rules to determine the relevant diagrams and can save a lot of time and effort in the diagram drawing process.

4. Are there any rules or guidelines for drawing Feynman diagrams?

Yes, there are certain rules and guidelines that need to be followed when drawing Feynman diagrams. These include conservation laws for energy, momentum, and charge, as well as Feynman rules for particle interactions. It is important to follow these rules to ensure the accuracy of the diagrams.

5. Are Feynman diagrams still used in modern physics?

Yes, Feynman diagrams are still widely used in modern physics, particularly in the field of quantum field theory. They provide a visual representation of particle interactions and are used to calculate the probabilities of various processes. However, computer programs have made the process of drawing diagrams more efficient and accurate.

Similar threads

I What is the probability of an electron emitting a photon?
    • Quantum Physics
Replies
14
Views
1K
I How to determine Spinor in Feynman diagram
    • Quantum Physics
Replies
6
Views
1K
I Diagrams for nucleon scattering
    • Quantum Physics
Replies
3
Views
2K
I Confusion about Scattering in Quantum Electrodynamics
    • Quantum Physics
4
Replies
134
Views
7K
I Calculating a particular amplitude with Feynman diagrams
    • Quantum Physics
Replies
2
Views
1K
I Building a List of Feynman Diagrams
    • Quantum Physics
Replies
3
Views
2K
A Scalar-scalar scattering Feynman diagram
    • Quantum Physics
Replies
7
Views
2K
A How to calculate Feynman amplitude in Fish diagram
    • High Energy, Nuclear, Particle Physics
Replies
2
Views
1K
I Scattering, 4 point correlator, number of distinct Feynman diagrams
    • Quantum Physics
Replies
15
Views
2K
ELI5: Antiparticles in Feynman Diagrams
    • Quantum Physics
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top