Oscillating Quintessence

Abstract

An oscillating scalar field as a quintessence model for dark energy is proposed. The case of a power-law potential is particularly intriguing and is the focus of the present article. In this model the equation of state w_{OQ} of dark energy is a constant determined simply by the power n in the potential through w_{OQ} = (n-2)/(n+2). Accordingly, when 0 < n < 1, the oscillating quintessence can provide repulsive gravity and drive the cosmic acceleration. The condition for oscillation and the constraints from observations are investigated. For this new scenario a specific natural model with much less fine tuning is presented.