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Coupled quintessence

Coupled quintessence A new component of the cosmic medium, a light scalar field or “quintessence,” has been proposed recently to explain cosmic acceleration with a dynamical cosmological constant. Such a field is expected to be coupled explicitly to ordinary matter, unless some unknown symmetry prevents it. I investigate the cosmological consequences of a coupled quintessence (CQ) model, assuming an exponential potential and a linear coupling. This model is conformally equivalent to Brans-Dicke Lagrangians with any power-law potential. I evaluate the density perturbations on the cosmic microwave background and on the galaxy distribution at the present and derive bounds on the coupling constant from the comparison with observational data. A novel feature of CQ is that during the matter dominated era the scalar field has a finite and almost constant energy density. This epoch, denoted as φMDE, is a saddle point in the dynamical phase space. The φMDE is responsible of several differences with respect to uncoupled quintessence: the multipole spectrum of the microwave background is tilted at large angles, the acoustic peaks are shifted, their amplitude is changed, and the present 8 Mpc/ h density variance is diminished. The present data constrain the dimensionless coupling constant to | β | <~ 0.1 assuming Ω m = 0.3 and a primordial fluctuation slope n s = 1. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review D American Physical Society (APS)

Coupled quintessence

Physical Review D , Volume 62 (4) – Aug 15, 2000
10 pages

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Publisher
American Physical Society (APS)
Copyright
Copyright © 2000 The American Physical Society
ISSN
1089-4918
DOI
10.1103/PhysRevD.62.043511
Publisher site
See Article on Publisher Site

Abstract

A new component of the cosmic medium, a light scalar field or “quintessence,” has been proposed recently to explain cosmic acceleration with a dynamical cosmological constant. Such a field is expected to be coupled explicitly to ordinary matter, unless some unknown symmetry prevents it. I investigate the cosmological consequences of a coupled quintessence (CQ) model, assuming an exponential potential and a linear coupling. This model is conformally equivalent to Brans-Dicke Lagrangians with any power-law potential. I evaluate the density perturbations on the cosmic microwave background and on the galaxy distribution at the present and derive bounds on the coupling constant from the comparison with observational data. A novel feature of CQ is that during the matter dominated era the scalar field has a finite and almost constant energy density. This epoch, denoted as φMDE, is a saddle point in the dynamical phase space. The φMDE is responsible of several differences with respect to uncoupled quintessence: the multipole spectrum of the microwave background is tilted at large angles, the acoustic peaks are shifted, their amplitude is changed, and the present 8 Mpc/ h density variance is diminished. The present data constrain the dimensionless coupling constant to | β | <~ 0.1 assuming Ω m = 0.3 and a primordial fluctuation slope n s = 1.

Journal

Physical Review DAmerican Physical Society (APS)

Published: Aug 15, 2000

There are no references for this article.