Abstract
We examine -essence models in which the Lagrangian is a function only of the derivatives of a scalar field and does not depend explicitly on . The evolution of for an arbitrary functional form for can be given in terms of an exact analytic solution. For quite general conditions on the functional form of , such models can evolve to a state characterized by a density scaling with the scale factor as , but with a sound speed at all times. Such models can serve as a unified model for dark matter and dark energy, while avoiding the problems of the generalized Chaplygin gas models, which are due to a non-negligible sound speed in these models. A dark-energy component with serves to suppress cosmic microwave background fluctuations on large-angular scales.
- Received 19 February 2004
DOI:https://doi.org/10.1103/PhysRevLett.93.011301
©2004 American Physical Society