Early-universe constraints on a Primordial Scaling Field
Abstract
In the past years 'quintessence' models have been considered which can produce the accelerated expansion in the universe suggested by astronomical observations. One of the key differences between quintessence and a cosmological constant is that the energy density in quintessence Omega_Q could be a significant fraction of the overall energy even in the early universe, while the cosmological constant will be relevant only at late times. We use standard Big Bang Nucleosynthesis and the observed abundances of primordial nuclides to put constraints on Omega_Q at temperatures near T = 1Mev. We point out that current experimental data does not support the presence of such a field, providing the strong constraint Omega_Q(MeV) < 0.045 at 2-sigma C.L. and strengthening previous results. We also consider the effect a scaling field has on CMB anisotropies providing the CMB constraint Omega_Q < 0.62 at 2-sigma C.L. in the radiation dominated epoch.Keywords
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