Parametrizing dark sector perturbations via equations of state

Battye, Richard A.; Pearson, Jonathan A.

Abstract

The evolution of perturbations is a crucial part of the phenomenology of the dark sector cosmology. We advocate parametrizing these perturbations using equations of state for the entropy perturbation and the anisotropic stress. For small perturbations, these equations of state will be linear in the density, velocity and metric perturbations, and in principle these can be related back to the field content of the underlying model allowing for confrontation with observations. We illustrate our point by constructing gauge-invariant entropy perturbations for theories where the dark sector Lagrangian is a general function of a scalar field, its first and second derivatives, and the metric and its first derivative, L=L(ϕ,∂μϕ,∂μ∂νϕ,gμν,∂αgμν). As an example, we show how to apply this approach to the case of models of kinetic gravity braiding.

Citation

Battye, R. A., & Pearson, J. A. (2013). Parametrizing dark sector perturbations via equations of state. Physical Review D, 88(6), Article 061301. https://doi.org/10.1103/physrevd.88.061301

• Journal Article Type: Article
• Publication Date: Sep 1, 2013
• Deposit Date: Jun 10, 2013
• Publicly Available Date: Mar 25, 2014
• Journal: Physical Review D - Particles, Fields, Gravitation, and Cosmology
• Print ISSN: 1550-7998
• Electronic ISSN: 1550-2368
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 88
• Issue: 6
• Article Number: 061301
• DOI: https://doi.org/10.1103/physrevd.88.061301
• Public URL: https://durham-repository.worktribe.com/output/1481908