Why does Principle for least action hold for classical fields
40340
How general is the Lagrangian quantization approach to field theory?
88525
Action and Action integral: Different kinds of variational principles
42036
Why should an action integral be stationary? On what basis did Hamilton state this principle?
106506
How to derive completeness relation in quantum field theory with a Lorentz invariant measure?
64424
Why does the classical path give the dominant contribution in the path integral?
153727
Constant term in Lagrangian
61686
Noether's first theorem and classical proof of electric charge conservation
125081
What is the reasoning that leads one to postulate this second form for the relativistic particle action?
115936
Is there a theorem that says that QFT reduces to QM in a suitable limit? A theorem similar to Ehrenfest's theorem?
42414
Why there is no unique "recipe" for quantization of a classical theory?
64228
D'Alemberts Principle to solve a Classical Mechanics problem
67641
Why should field operators satisfy the classical equations of motion?
114910
In what subfields and how far can the naive limit $c\rightarrow\infty$ of special relativity be carried?
105660
Invariance of action $\Rightarrow$ covariance of field equations?
100004
Differentiating $e^x$ from first principles using limits.
10785
Form of the Classical EM Lagrangian
57051
Why does Quantum Field Theory use Lagrangians rather than Hamiltonians?