# Tag Info

## New answers tagged locality

-1

No, global symmetries are not at odds with local field theory, since the global transformations are just gauge transformations that are constant in space and time, and are thus naturally a subset of the gauge transformations. Gauge symmetries thus include a global symmetry. All these quotes intend to say is to provide a heuristic for why the relaxation from ...

0

I believe this apparent contradiction to stem from a misunderstanding that energy can be transferred only by the one mechanism to which the Poynting vector applies: The Poynting vector is defined as ExH, and applies to a "launched" electromagnetic wave in propagation. In your example, the energy is being transferred by a quasi-static E-field in the absence ...

0

For a classical field theory or a classical field and particle theory you want the dynamics of that stationary path. (Or the dynamics of one of the stationary paths.) But you consider all kinds of dynamics, and just reject the ones that don't have a stationary action. If you know the Euler-Lagrange equations you are aiming for are going to just have/be ...

3

The vector potential of an oscillating dipole (using the usual electric dipole approximation) can be written as $$\vec{A} =\frac{\mu_0 I_0 l}{4\pi r} \cos \omega(t-r/c)\ \hat{z},$$ where the dipole is of length $l$, with a current $I_0 \cos \omega t$ and $\hat{z}$ is a unit vector along the z-axis of the dipole. Using the Lorenz gauge one can then ...

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