Local short-time acceleration induced spectral line broadening and possible implications in cosmology

Abstract

The paper proposes an acceleration effect that a local short-time acceleration produces an additional broadening to spectral line, while the central value of the line remains unaffected. The effect can be considered as a local and non-uniform generalization of Unruh effect. Although the acceleration-induced line broadening effect is too small to be measured in ordinary lab setup, it may offer us a key concept to gain a simple and unified perspective on the cosmic acceleration and the radial acceleration discrepancy of rotating galaxies. We find that the measurement of the acceleration of the cosmic expansion by fitting the distance-redshift relation is essentially the measurement of the line or redshift broadening, and the cosmic acceleration induced line broadening also plays a crucial role in the acceleration discrepancy at the outskirt of rotating galaxies. Possible predictions of the effect are also discussed.