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I'm my current studies in Noether's theorem, the two that I liked the most are joshphysics answer to this Phys SE. post, and the derivation in chapter $4$ of An Elementary Introduction to Classical Fields by R. Aldrovandi and J. G. Pereira. Johphysics answer is nice because he introduces a notion of variation of a field $\delta \phi$ as derivative of a flow instead of the usual treatment of "infinitesimals". He derives Noether's theorem only using what is called "functional variations", wich does not change the integration domain of an action functional $S[\phi]$, and affects only the functional form of the fields and its lagrangian $\mathcal{L}(\phi(x), \partial_\mu \phi(x))$.

Aldrovandi, however, even using the notion of variations as "infinitesimas", make clear statements about what is going on. Specifically in equations $4.16 - 4.18$, he defines the coordinate variation as well as total and functional variation of fields $\phi(x)$. And states in the paragraph before page 98 the following:

Let us go back to the action functional $(4.15)$. It does not depend on x. Its is a functional of the elds, depending on the integration domain. Variations $(4.16)$ and $(4.17)$ will have eects of two kinds: changes in the integration volume and in the Lagrangian density. We shall indicate this by writing $$ \delta A[\phi] = \int [\delta(d^4x)\mathcal{L} + d^4x \delta \mathcal{L}]$$

In Aldrovandi, the term $\delta\mathcal{L}$ is used as a total variation, wich is different from the definition of $\delta \mathcal{L}$ used by johphysics.

The result of what is called Noether's first theorem is given by the equation

$$\partial_\mu J^\mu = 0,$$ which is the same for both derivations, but one uses only variation of functional form of fields, and the other uses contributions due to coordinate change, how is that possible?

Qmechanic
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