title: Axion dark matter and cosmological parameters.
abstract: We observe that photon cooling after big bang nucleosynthesis but before recombination can remove the conflict between the observed and theoretically predicted value of the primordial abundance of ^{7}Li. Such cooling is ordinarily difficult to achieve. However, the recent realization that dark matter axions form a Bose-Einstein condensate provides a possible mechanism because the much colder axions may reach thermal contact with the photons. This proposal predicts a high effective number of neutrinos as measured by the cosmic microwave anisotropy spectrum.
authors.affiliation: Department of Physics, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: O
authors.initials: O
authors.lastname: Erken
authors.forename: P
authors.initials: P
authors.lastname: Sikivie
authors.forename: H
authors.initials: H
authors.lastname: Tam
authors.forename: Q
authors.initials: Q
authors.lastname: Yang