Effects of the Sound Speed of Quintessence on the Microwave Background

 and Large Scale Structure

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

We consider how quintessence models in which the sound speed differs from the speed of light and varies with time affect the cosmic microwave background and the fluctuation power spectrum. Significant modifications occur on length scales related to the Hubble radius during epochs in which the sound speed is near zero and the quintessence contributes a non-negligible fraction of the total energy density. For the microwave background, we find that the usual enhancement of the lowest multipole moments by the integrated Sachs-Wolfe effect can be modified, resulting in suppression or bumps instead. Also, the sound speed can produce oscillations and other effects at wavenumbers \(k > 10^{-2}\) h/Mpc in the fluctuation power spectrum.

Related collections

Most cited references 14

Record: found
Abstract: found
Article: found

Is Open Access

Cosmological Imprint of an Energy Component with General Equation of State

Rahul Dave, Paul J. Steinhardt, R. Caldwell (1997)

We examine the possibility that a significant component of the energy density of the universe has an equation-of-state different from that of matter, radiation or cosmological constant (\(\Lambda\)). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this component alters cosmic evolution in a way that fits current observations well. Unlike \(\Lambda\), it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.

0 comments Cited 479 times – based on 0 reviews

Preprint

     Review now

Bookmark

Record: found
Abstract: found
Article: found

Is Open Access

Quintessence, Cosmic Coincidence, and the Cosmological Constant

Ivaylo Zlatev, Paul J. Steinhardt, Limin Wang (1998)

Recent observations suggest that a large fraction of the energy density of the universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a scalar field slowly evolving down a potential. In either case, a key problem is to explain why the energy density nearly coincides with the matter density today. The densities decrease at different rates as the universe expands, so coincidence today appears to require that their ratio be set to a specific, infinitessimal value in the early universe. In this paper, we introduce the notion of a "tracker field", a form of quintessence, and show how it may explain the coincidence, adding new motivation for the quintessence scenario.

0 comments Cited 254 times – based on 0 reviews

Preprint

     Review now

Bookmark

Record: found
Abstract: found
Article: found

Is Open Access

A Dynamical Solution to the Problem of a Small Cosmological Constant and Late-time Cosmic Acceleration

Paul J. Steinhardt, V. Mukhanov, C. Armendáriz-Picón (2000)

Increasing evidence suggests that most of the energy density of the universe consists of a dark energy component with negative pressure, a ``cosmological constant" that causes the cosmic expansion to accelerate. In this paper, we address the puzzle of why this component comes to dominate the universe only recently rather than at some much earlier epoch. We present a class of theories based on an evolving scalar field where the explanation is based entirely on internal dynamical properties of the solutions. In the theories we consider, the dynamics causes the scalar field to lock automatically into a negative pressure state at the onset of matter-domination such that the present epoch is the earliest possible time, consistent with nucleosynthesis restrictions, when it can start to dominate.