Tagged Questions
2
votes
1answer
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Constructing the “most general” two-particle spin interaction with $SU(2)$ symmetry
Suppose I want to write down an interaction term for an action for spin 1/2 fermions that is $SU(2)$-symmetric.
I start from the most naive general form of such an action:
$$S_{int} ~=~ \int_{4321} ...
3
votes
3answers
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Calculating lagrangian density from first principle
In most of the field theory text they will start with lagrangian density for spin 1 and spin 1/2 particles. But i could find any text where this lagrangian density is derived from first principle.
