Generally covariant geometric momentum, gauge potential and a Dirac fermion on a two-dimensional sphere

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2019-08, Vol.79 (8), p.1-8, Article 712
• Main Authors: Liu, Q. H., Li, Z., Zhou, X. Y., Yang, Z. Q., Du, W. K.
• Format: Article
• Language: English
• Subjects: Angular momentum; Astronomy; Astrophysics and Cosmology; Cartesian coordinates; Curvature; Elementary Particles; Fermions; Hadrons; Heavy Ions; Hyperspaces; Hyperspheres; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Particle spin; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; String Theory
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-019-7231-4

For a particle that is constrained on an ( N - 1 )-dimensional ( N ≥ 2 ) curved surface Σ N - 1 , the Cartesian components of its momentum in N -dimensional flat space are believed to offer a proper form of momentum for the particle on the surface, which is called the geometric momentum as it depends on the mean curvature. Once the momentum becomes generally covariant as to be applicable to spin particles on the surface, the spin connection part in it can be interpreted as a gauge potential. The principal findings are twofold. The first is a general framework of quantum conditions for a spin particle on the hypersurface Σ N - 1 , and the generalized angular momentum is defined on hypersphere S N - 1 as one consequence of the generally covariant geometric momentum. The second is devoted to a study of a Dirac fermion on a two-dimensional sphere and we show that there is the generalized angular momentum whose three cartesian components form the su (2) algebra, demonstrated to be of geometric origin but obtained before by consideration of dynamics of the particle. Moreover, we show that there is no curvature-induced geometric potential for the spin half particle.