In very asymmetric potentials, like atoms in crystals, this quantity is “quenched” and has expectation value zero. A 1992 paper by Allen et al. pioneered the study of a form of this quantity carried by Laguerre-Gaussian modes and useful for high-capacity communication, as it has theoretically infinite multiplexing channels. A classical analogue of this quantity carried by light can be any integer and describes its phase distribution, while a related quantity describes its polarization. For (*) spherically symmetric potentials, the Hamiltonian commutes with both this quantity squared (10[1])and its (10[1])projection (10[2])along the z-axis. (10[1])The squared magnitude of this quantity is h-bar-squared times azimuthal number times azimuthal number plus one. (10[1])For 10 points, name this quantity that is conserved in rotationally (10[2])symmetric (10[2])systems. ■END■