Quintessence and tachyon dark energy models with a constant equation of state parameter

Abstract

In this work we determine the correspondence between quintessence and tachyon dark energy models with a constant dark energy equation of state parameter, $w_e$. Although the evolution of both the Hubble parameter and the scalar field potential with redshift is the same, we show that the evolution of quintessence/tachyon scalar fields with redshift is, in general, very different. We explicity demonstrate that if $w_e\ne -1$ the potentials need to be very fine-tuned for the relative perturbation on the equation of state parameter, $\Delta w_e/(1+w_e)\ll 1$, to be very small around the present time. We also discuss possible implications of our results for the reconstruction of the evolution of $w_e$ with redshift using varying couplings.

9 pages, 2 figures, published version with two extra references included

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• The van der Waals fluid and its role in cosmology
• Tachyonic cosmology with cubic contractions of the Riemann tensor
• Generalized Layzer-Irvine equation: the role of dark energy perturbations in cosmic structure formation
• Primordial scalar perturbations in tachyonic power-law inflation
• Chi-square versus median statistics in SNIa data analysis
• Lorentzian wormholes supported by tachyon matter
• Linking phantom quintessences and tachyons
• Assessing the viability of successful reconstruction of the dynamics of dark energy using varying fundamental couplings
• Avoiding unrealistic priors: the case of dark energy constraints from the time variation of the fine-structure constant