Question #66689

1 Answer
Chitram Banerjee
Apr 23, 2016

Both the formalism have their own pros:

Lagrangian density is inherently symmetric in terms of space and time as they bring them to equal footing. Hence, it is better to use it for QFT, and also it is easier to work with path integrals with L in QFT.

Whereas, Hamiltonian density explicitly shows the unitarity of evolution of a QM process, hence making it the choice for non-relativistic case.

Hope this helps.

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