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Vector potentials

How many vector fields admit a certain vector potential?
Original post by JrW13
How many vector fields admit a certain vector potential?


Do you mean: given AA, for how many fields BB is it true that B=×AB=\nabla \times A?
Reply 2
Yes
Original post by JrW13
How many vector fields admit a certain vector potential?


Recall, as we saw in this thread, that

×A=×(A+ϕ)\displaystyle \nabla \times A = \nabla \times (A + \nabla \phi)

for some scalar function ϕ\phi. Now recall that a vector field is irrotational if and only if it admits a scalar potential. Put these two facts together and you get the answer.
Original post by Gregorius
Recall, as we saw in this thread, that

×A=×(A+ϕ)\displaystyle \nabla \times A = \nabla \times (A + \nabla \phi)

for some scalar function ϕ\phi. Now recall that a vector field is irrotational if and only if it admits a scalar potential. Put these two facts together and you get the answer.


You seem to have answered the inverse question, AFAICS: how many vector potentials does a certain vector field admit?
Original post by atsruser
You seem to have answered the inverse question, AFAICS: how many vector potentials does a certain vector field admit?


Ooh yes...could be. But is the inverse of this even a question?
Original post by Gregorius
Ooh yes...could be. But is the inverse of this even a question?


It's a pretty boring one, I think, since differentiation isn't multivalued, but the OP answered my clarifying question with a yes. I've got a feeling that the setter or the OP posed the question incorrectly, and it's really meant to be the one that you asked.

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