title: Measuring the primordial deuterium abundance during the cosmic dark ages.
abstract: We discuss how measurements of fluctuations in the absorption of cosmic microwave background photons by neutral gas at redshifts z approximately 7-200 could reveal the primordial deuterium abundance of the Universe. The strength of the cross-correlation of brightness-temperature fluctuations in the redshifted 21-cm line of hydrogen with those in the redshifted 92-cm line of deuterium is proportional to the value of the deuterium-to-hydrogen ratio [D/H] fixed during big bang nucleosynthesis. Although challenging, this measurement would provide the cleanest possible determination of [D/H], free from contamination by structure formation processes at lower redshifts. We additionally report our result for the thermal spin-change cross section in deuterium-hydrogen scattering.
authors.affiliation: California Institute of Technology, Mail Code 130-33, Pasadena, California 91125, USA. ksigurds@tapir.caltech.edu
authors.forename: Kris
authors.initials: K
authors.lastname: Sigurdson
authors.forename: Steven R
authors.initials: SR
authors.lastname: Furlanetto