why does spin-orbit coupling have a positive and negative sign?
What exactly are you referring to?
the spin orbit coupling in atoms that have more than one electron in modern physics...
That part was obvious but were you referring to a specific formula like the SO-hamiltonian or something?
no.... sorry!!! my mistake!!! it's why does the z component of the spin angular momentum have a positive and negative sign?
You mean the eigenvalues, right...? Well, basically, group theory explains why...
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