We show that the angular directions locally measured by a static geodesic observer in a generic cosmological background and expressed in the system of Fermi Normal Coordinates always coincide with those expressed in the Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits the residual gauge freedom of the GLC coordinates. This is not the case for other gauges | like, for instance, the synchronous and longitudinal gauge | commonly used in the context of observational cosmology. We also make an explicit proposal for the GLC gauge-fxing condition that ensures a full identifcation of its angles with the observational ones.
Observation angles, Fermi coordinates, and the Geodesic-Light-Cone gauge
Gasperini, M.;
2019-01-01
Abstract
We show that the angular directions locally measured by a static geodesic observer in a generic cosmological background and expressed in the system of Fermi Normal Coordinates always coincide with those expressed in the Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits the residual gauge freedom of the GLC coordinates. This is not the case for other gauges | like, for instance, the synchronous and longitudinal gauge | commonly used in the context of observational cosmology. We also make an explicit proposal for the GLC gauge-fxing condition that ensures a full identifcation of its angles with the observational ones.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
