From Effective Lagrangian to Feynman Rule

In summary, the conversation discusses the calculation of the amplitude using the interaction Lagrangian N*→N+photon. It is mentioned that if the functional method is used, the field operator is not polynomial and the "center formula" must be used to bring the functional derivative in. Alternatively, the field operator can be expanded into annihilation and creation operators to obtain the amplitude. The speaker also mentions uncertainty in writing Feynman rules for this Lagrangian using the path integral formalism and suggests using the canonical expression for the fields and working with creation and annihilation operators instead.
  • #1
zhangyang
58
0
In this process:

N*→N+photon

If we want to calculate the amplitude with the following interaction Lagrangian:

upload_2015-4-5_14-34-39.png


(http://arxiv.org/abs/nucl-th/0205052)

If we use functional method,the field operator is not polynomial,how to use "center formula"to bring functional derivative in? Or we must drop functional method,and use expension of field operator into annihilation and creation operator to get amplitude ?
 
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  • #2
I honestly don't know how to write the Feynman rules for such a Lagrangian with the path integral formalism. Personally I always found much easier to simply use the canonical expression for the fields and from there write down the rules starting from the creation and annihilation operators.
 

Related to From Effective Lagrangian to Feynman Rule

1. What is an effective Lagrangian?

An effective Lagrangian is a mathematical framework used in particle physics to describe the interactions between particles. It is derived from a more fundamental Lagrangian, but takes into account the effects of higher energy processes and integrates them into a single, simplified equation.

2. How is an effective Lagrangian used to derive Feynman rules?

The effective Lagrangian serves as a starting point for calculating Feynman diagrams, which are graphical representations of particle interactions. By using mathematical techniques such as perturbation theory, Feynman rules can be derived from the effective Lagrangian, allowing for the prediction of particle behavior and interactions.

3. What are Feynman rules?

Feynman rules are a set of mathematical rules and diagrams used to calculate the probability of interactions between particles. They are derived from the effective Lagrangian and are essential in making predictions about particle behavior in particle physics experiments.

4. How do effective Lagrangians and Feynman rules help us understand particle interactions?

Effective Lagrangians and Feynman rules are powerful tools in particle physics as they enable us to make predictions about the behavior of particles and their interactions. By using these mathematical frameworks, we can gain a deeper understanding of the fundamental forces that govern the universe.

5. Are effective Lagrangians and Feynman rules applicable to all particle interactions?

Effective Lagrangians and Feynman rules are applicable to most particle interactions, but they may not accurately describe interactions at very high energies or in extreme conditions such as those found in black holes. Additionally, they may not apply to interactions involving particles that have not yet been discovered or fully understood.

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