Parametrizing dark sector perturbations via equations of state

Battye, Richard A.; Pearson, Jonathan A.

doi:10.1103/physrevd.88.061301

Parametrizing dark sector perturbations via equations of state

Battye, Richard A.; Pearson, Jonathan A.

Authors

Richard A. Battye

Jonathan A. Pearson

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
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

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Copyright Statement
Reprinted with permission from the American Physical Society: Battye, Richard A. and Pearson, Jonathan A. (2013) 'Parametrizing dark sector perturbations via equations of state.', Physical review D : particles, fields, gravitation, and cosmology., 88 (6). 061301 © 2013 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.