Massless fermions in spatially flat FLRW space-times

Abstract

Abstract The propagation of the packets of left-handed plane wave solutions of the massless Dirac equation is studied in spatially flat Friedmann–Lemaître–Robertson–Walker (FLRW) space-times. Assuming that the observations are performed in physical frames with Painlevé–Gullstrand coordinates, the current and energy–momentum tensor are derived, emphasising their severe decay and moderate dispersion during propagation. As the wave packets move along null geodesics, interesting effects are produced by the apparent or event horizons.