2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/155051Quasi-classical picture of motion of spin 1/2 massless particle in a curved spacetime is built on base of simple Lagrangian model. The one is constructed due to analogy with Lagrangian of massive spin 1/2 particle. Equations of motion and spin propagation coincide with Papapetrou equations describing dynamic of photon in a curved spacetime.7 pagesGeneral Relativity and Quantum Cosmologytext