Due to the Helmholtz decomposition theorem, Gauss's law for magnetism is equivalent to the following statement:[5][6]
There exists a vector field A such thatmathbf{B} =
abla imesmathbf{A}.
The vector field A is called the magnetic vector potential.
Note that there is more than one possible A which satisfies this equation for a given B field. In fact, there are infinitely many: any field of the form ∇φ can be added onto A to get an alternative choice for A, by the identity