SU (2) particle sigma model: the role of contact symmetries in global quantization

In this paper we achieve the quantization of a particle moving on the SU (2) group manifold, that is, the three-dimensional sphere S ³, by using group-theoretical methods. For this purpose, a fundamental role is played by contact symmetries, i.e., symmetries that leave the Poincaré–Cartan form semi-invariant at the classical level, although not necessarily the Lagrangian. Special attention is paid to the role played by the basic quantum commutators, which depart from the canonical, Heisenberg–Weyl ones, as well as the relationship between the integration measure in the Hilbert space of the system and the non-trivial topology of the configuration space. Also, the quantization on momentum space is briefly outlined. (paper)