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Can we distinguish early dark energy from a cosmological constant?

Shi, D. and Baugh, C. M. (2016) 'Can we distinguish early dark energy from a cosmological constant?', Monthly notices of the Royal Astronomical Society., 459 (4). pp. 3540-3550.


Early dark energy (EDE) models are a class of quintessence dark energy with a dynamically evolving scalar field which display a small but non-negligible amount of dark energy at the epoch of matter-radiation equality. Compared with a cosmological constant, the presence of dark energy at early times changes the cosmic expansion history and consequently the shape of the linear theory power spectrum and potentially other observables. We constrain the cosmological parameters in the EDE cosmology using recent measurements of the cosmic microwave background and baryon acoustic oscillations. The best-fitting models favour no EDE; here we consider extreme examples which are in mild tension with current observations in order to explore the observational consequences of a maximally allowed amount of EDE. We study the non-linear evolution of cosmic structure in EDE cosmologies using large-volume N-body simulations. Many large-scale structure statistics are found to be very similar between the Λ cold dark matter (ΛCDM) and EDE models. We find that EDE cosmologies predict fewer massive haloes in comparison to ΛCDM, particularly at high redshifts. The most promising way to distinguish EDE from ΛCDM is to measure the power spectrum on large scales, where differences of up to 15 per cent are expected.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:12 April 2016
Date deposited:16 June 2016
Date of first online publication:15 April 2016
Date first made open access:16 June 2016

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