Feshbach-Villars Formalism for a Spin-1/2 Particle in Curved Spacetime

This study explores the Feshbach-Villars (FV) formalism for spin-1/2 particles in curved spacetime. We derive the Hamiltonian form of the Dirac equation in this context and extend the FV transformation accordingly. The generalized Klein-Gordon equation, obtained by squaring the Dirac operator, is reformulated using the FV approach. We present the resulting Hamiltonian in both matrix and Pauli matrix forms, considering gravitational and electromagnetic interactions. The formalism is examined in both (1+2) and (1+3) dimensional spacetimes, with special attention given to the spin-field interaction term. This study provides a framework for studying relativistic quantum mechanics in curved spacetime, offering insights into the interplay between quantum effects, gravity, and electromagnetism.