The canonical momentum is defined as
pi=∂L∂˙qi, where L is the Lagrangian.
So actually how does pi transform in one coordinate system q to another coordinate system Q ?
http://en.wikipedia.org/wiki/Hamiltonian_mechanics#Charged_particle_in_an_electromagnetic_field
When dealing with the Hamiltonian of the electromagnetic field, the derivation of pj=m˙xj+eAj on the above link is usually written as p=mv+eA
but the derivation is based on using Cartesian coordinates, does it mean that p is really a vector? If we are using another general coordinates, say, spherical coordinates, can we still have p=mv+eA ? If no, I think the form of Hamiltonian in electromagnetic field
H=(p−eA)22m+eϕ
will only be valid in Cartesian coordinates. In any other coordinates, H carries a different form!
Any comments are appreciated.
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