The Quantum Lagrangian

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    One of the most fundamental laws of physics is the principle of least action, the statement that between any two events the elements that attend those events (particles and fields) must act out the least action possible in the circumstances. The key concept in that statement is the Lagrangian function that we associate with the particles and fields. Proper manipulation of that function gives us descriptions of the basic laws of physics, classical, thermodynamic, and relativistic. We also expect that a suitable Lagrangian will give us the laws of the quantum theory. To the end of finding such a Lagrangian, the following sub-essays look at the relativistic quantum theory:

GO TO: The Principle of Least Action

GO TO: The Dirac Form

GO TO: The Proca Form

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