Can we ever distinguish between quintessence and a cosmological constant?

Abstract

Many ambitious experiments have been proposed to constrain dark energy and detect its evolution. At present, observational constraints are consistent with a cosmological constant and there is no firm evidence for any evolution in the dark energy equation of state w. In this paper, we pose the following question: suppose that future dark energy surveys constrain w at low redshift to be consistent with −1 to a percent level accuracy, what are the implications for models of dynamical dark energy? We investigate this problem in a model-independent way by following quintessence field trajectories in 'energy' phase-space. Attractor dynamics in this phase-space leads to two classes of acceptable models: 1) models with flat potentials, i.e. an effective cosmological constant, and 2) models with potentials that suddenly flatten with a characteristic kink. The prospect of further constraining the second class of models from distance measurements and fluctuation growth rates at low redshift (z 3) seems poor. However, in some models of this second class, the dark energy makes a significant contribution to the total energy density at high redshift. Such models can be further constrained from observation of the cosmic microwave background anisotropies and from primordial nucleosynthesis. It is possible, therefore, to construct models in which the dark energy at high redshift causes observable effects, even if future dark energy surveys constrain w at low redshift to be consistent with −1 to high precision.

Falsifying Paradigms for Cosmic Acceleration

“…Our study complements previous work [29,30,31] on the observable predictions of classes of dark energy models, and follows a long history of studies concerning the best way to probe dark energy using cosmological observations [32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70]. To our knowledge this is the first time that consistency between growth, distance, and other expansion observables has been studied in such a general and quantitative way.…”

Stochastic quintessence models: Jerk and fine-structure variability constraints

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We report on constraints to the cosmological jerk parameter (j) and to possible variability of the fine-structure constant (∆α/α) based on stochastic quintessence models of dark energy, discussed by Chongchitnan and Efstathiou (2007). We confirm the results by these authors in the sense that many viable solutions can be obtained, obeying current observational constraints in low redshifts.

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AIC, BIC, Bayesian evidence against the interacting dark energy model

“…We share George Efstathiou's opinion [41][42][43] that there is no sound theoretical basis for considering dynamical dark energy, whereas we are beginning to see an explanation for a small cosmological constant emerging from a more fundamental theory. In our opinion the CDM model has the status of a satisfactory effective theory.…”