Action principles and covariant equations
44282
How do I show that there exists variational/action principle for a given classical system?
121494
Invariance, covariance and symmetry
87125
Does action really have to be Lorentz-invariant in SR?
69199
How to find the continuous transformations which leave the action invariant?
67641
Why should field operators satisfy the classical equations of motion?
33868
A transformation between two free group actions.
63098
Properly discontinuous actions and discrete groups in complete Riemannian manifolds.
152446
Noether's Theorem and scale invariance
61530
Definitions and usage of Covariant, Form-invariant & Invariant?
70880
Invariance of canonical Hamiltonian equation when adding the total time derivative of a function of $q_i$ and $t$ to the Lagrangian
94041
Interpretation Born-Von Karman boundary conditions
258
Existence of orthogonal coordinates on a Riemannian manifold
983
Use partial or covariant derivatives when deriving equations of a field theory?
67357
Geodesics equations via variational principle
27490
Group Theory in General Relativity
99063
Einstein-Hilbert action as an effective field theory
120529
Relations between diffeomorphism symmetry theories and invariant $SU(N), N \rightarrow \infty$ theories