- #1

Pouramat

- 28

- 1

**Summary::**Can anyone introduce an informative resource with solved examples for learning variation principle?

For example I cannot do the variation for the electromagnetic lagrangian when ##A_\mu J^\mu## added to the free lagrangian and also some other terms which are possible:

$$

L = \sqrt{-g}(\frac{-1}{4}F^{\mu \nu}F_{\mu \nu}+A_\mu J^\mu)

$$

also I want to add ##L' = \beta R^{\mu \nu} g^{\rho \sigma}F_{\mu \rho}F_{\nu \sigma}## to lagrangian and then do the variation to see what is the difference, but I cannnot.

Do you know any good resources to understand with solved examples?