Phy5646/character

Angular Momentum Addition by Characters

Rotation matrices $e^{{\mathit {i}}{{\vec {\omega }}.{\vec {J}}}}$ are $(2{\mathit {j}}+1)\times (2{\mathit {j}}+1)$ matrix functions of rotating angles ${\vec {\omega }}$ in some representation of spin ${\mathit {j}}$. To indicate more explicitly the representation we are in we write them as $D_{\mathit {j}}({\vec {\omega }})$.