The Lagrangian formulation, in essence, describes the dynamics of a particle starting with the action principle. Through the so–called Euler–Lagrange equations it allows one to determine the particle’s equations of motion. One of the properties of a Lagrangian is that the conservation laws can be incorporated through it quite simply. It is important to note that the action principle also plays a role in quantum mechanics through Feynman path integral techniques.

In the path integral technique in quantum mechanics, the concept of a unique path for a classical particle is replaced, starting from the superposition principle, by a sum of infinitely many possible paths that a particle can take between ...

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