Spin and maximal acceleration

We study the spin current tensor of a Dirac particle at accelerations close to the upper limit introduced by Caianiello. Continual interchange between particle spin and angular momentum is possible only when the acceleration is time-dependent. This represents a stringent limit on the effect that maximal acceleration may have on spin physics in astrophysical applications. We also investigate some dynamical consequences of maximal acceleration.Comment: 8 page

Perspectives on gravity-induced radiative processes in astrophysics

Single-vertex Feynman diagrams represent the dominant contribution to physical processes, but are frequently forbidden kinematically. This is changed when the particles involved propagate in a gravitational background and acquire an effective mass. Procedures are introduced that allow the calculation of lowest order diagrams, their corresponding transition probabilities, emission powers and spectra to all orders in the metric deviation, for particles of any spin propagating in gravitational fields described by any metric. Physical properties of the "space-time medium" are also discussed. It is shown in particular that a small dissipation term in the particle wave equations can trigger a strong back-reaction that introduces resonances in the radiative process and affects the resulting gravitational background.Comment: 8 pages, one figure. arXiv admin note: substantial text overlap with arXiv:1007.483

Gravitational qubits

We report on the behaviour of two-level quantum systems, or qubits, in the background of rotating and non-rotating metrics and provide a method to derive the related spin currents and motions. The calculations are performed in the external field approximation.Comment: 16 pages. arXiv admin note: text overlap with arXiv:0709.0819, arXiv:gr-qc/050302

Helicity Precession of Spin-1/2 Particles in Weak Inertial and Gravitational Fields

We calculate the helicity and chirality effects experienced by a spin-1/2 particle subjected to classical electromagnetic and gravitational fields. The helicity evolution is then determined in the non-relativistic, relativistic, and ultra-relativistic regimes. We find that inertia-gravitation can distinguish between helicity and chirality. Helicity is not conserved, in general, even when the particles are massless. In this case, however, the inertial fields can hardly be applied to the fermions.Comment: 17 pages with no figures. Submitted to Nuclear Physics