Principles of Quantum Mechanics · Problem 15.2.6

Addition of Angular Momenta — R. Shankar

Physics — Quantum Mechanics · projection-operators-L-plus-S

Problem

Construct the projection operators

\mathbb{P}_{\pm}

for the

j = l\pm 1/2

subspaces in the addition

\mathbf{L}+\mathbf{S}=\mathbf{J}