Question

Magnetic flux density and magnetic potential curl equation

Answer 1

A(r)=μ04πr3m×rA(r)=μ04πr3m×r

B(r)=∇×A=μ04πr3(3r(m⋅r)r2−m)B(r)=∇×A=μ04πr3(3r(m⋅r)r2−m)

Secondly, how and why the vector potential described in the above link different from one of the "retarded potentials" shown here. They're both used to find B(r), right?

A(r,t)=μ04π∫J(r′,tr)|r−r′|d3r′A(r,t)=μ04π∫J(r′,tr)|r−r′|d3r′

where tt=t−1c|r−r′|