4π spinor symmetry — some new observations

Abstract

With the help of analogous experiments with light polarization in an optical interferometer we demonstrate (i) an experimental situation where the rotation of a spin-Image wavefunction through 2π results in a phase change of 0 or −2π and not ±π, (ii) that in the conventional situation the phase change under 2π rotations is +π or −π depending upon whether the rotating state is in one or the other hemisphere on the state sphere.