paper

Fermionic Particle Creation in Curved Spacetime: Physical Bloch-Vector Dynamics and Exact de Sitter Scaling

arXiv:2610.00410 · doi:10.1016/j.aop.2026.170733

Abstract

We formulate fermionic particle creation in a time-dependent curved spacetime as the exact evolution of a physical Bloch vector. Each Dirac momentum mode reduces to a two-level system, and its instantaneous occupation is obtained by projecting the physical state onto the instantaneous energy basis. This construction is equivalent to the standard Bogoliubov description while retaining the complete finite-time state trajectory in a compact real geometry. It also makes the fermionic occupation bound manifest without attributing its microscopic origin to geometry alone. For a massive Dirac field in de Sitter spacetime, the dynamics reduces to a universal function of the physical momentum in Hubble units and the mass-to-Hubble ratio. We identify a mass-controlled nonadiabatic scale and a singular small-mass boundary layer that resolves the noncommuting massless and late-time limits. Independent Cartesian Bloch, angular Bloch, and Bogoliubov integrations verify the analytical results and recover the standard Gibbons--Hawking Fermi--Dirac plateau.

35 pages, 4 figures. Published in Annals of Physics 495 (2026) 170733

References in corpus (8)