A new class of cosmological quintessence models

We propose a new class of quintessence models in which late times oscillations of a scalar field give rise to an effective equation of state which can be negative: wφ ≤ −1/3, and hence drive the observed acceleration of the universe. Currently favoured values Ωφ ∼ 0.7, ΩCDM ∼ 0.3 inferred from observations of high redshift supernovae can be easily accommodated by our model. A novel feature of our ansatz is that it permits a unified treatment of quintessence and CDM, and might also provide a possible resolution of the core density problem for CDM halo’s. Additionally, since the quintessence field rolls to small values at late times, some possible constraints to slow-roll quintessence potentials can safely be ignored in our model. Quintessence potentials of the kind discussed in this paper are often encountered in field theory, condensed matter physics and particle physics.