The correct expression of the Euler-Lagrange equation in Field Theory
63473
Is the shorthand $ \partial_{\mu} $ strictly a partial derivative in field theory?
30992
How do you determine the Lagrangian?
125647
Solutions to the matrix equation $\mathbf{AB-BA=I}$ over general fields
51294
Derivation of Euler's equations for rigid body rotation
94173
Deriving the Lagrangian for a free particle
145835
Closed form for CRT solution using Euler $\phi\,$ (totient)
41407
How to derive or justify the expressions of momentum operator and energy operator?
13644
Is the change in the Lagrangian always a total derivative for symmetry transformations of the action?
105660
Invariance of action $\Rightarrow$ covariance of field equations?
82135
Lagrangian to Hamiltonian in Quantum Field Theory
153727
Constant term in Lagrangian
27296
Derivation of Lagrangian of electromagnetic field from Lorentz force
10953
Elementary argument for conservation laws from symmetries *without* using the Lagrangian formalism
124863
Performing Wick Rotation to get Euclidean action of a scalar field $\Psi$
56614
Why do the counterterms in renormalized $\phi^4$-theory with power two in fields give vertices and not propagators?
47230
A change of variables in the euler equation
127274
Textbook on QFT in curved space-time via path integrals