Purely Kinetic k Essence as Unified Dark Matter

Robert J. Scherrer
Phys. Rev. Lett. 93, 011301 – Published 30 June 2004

Abstract

We examine k-essence models in which the Lagrangian p is a function only of the derivatives of a scalar field φ and does not depend explicitly on φ. The evolution of φ for an arbitrary functional form for p can be given in terms of an exact analytic solution. For quite general conditions on the functional form of p, such models can evolve to a state characterized by a density ρ scaling with the scale factor a as ρ=ρ0+ρ1(a/a0)3, but with a sound speed cs21 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 cs1 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

Authors & Affiliations

Robert J. Scherrer

  • Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA

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Issue

Vol. 93, Iss. 1 — 2 July 2004

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