Twinlike models for parametrized dark energy
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Regular Article - Theoretical Physics
Twinlike models for parametrized dark energy J. D. Dantas1,a , J. J. Rodrigues2,b 1 2
Unidade Acadêmica de Física e Matemática, Universidade Federal de Campina Grande, Cuité, PB 58175-000, Brazil Departamento de Física, Universidade Estadual da Paraíba, Araruna, PB 58233-000, Brazil
Received: 31 March 2020 / Accepted: 12 July 2020 © The Author(s) 2020
Abstract We study cosmological models involving a single real scalar field that has an equation of state parameter which evolves with cosmic time. We highlight some common parametrizations for the equation of state as a function of redshift in the context of twinlike theories. The procedure is used to introduce different models that have the same acceleration parameter, with the very same energy densities and pressure in flat spacetime.
1 Introduction Cosmological observations of Type Ia Supernovae and Cosmic Microwave Background suggest that the Universe had started to accelerate its expansion at the present epoch [1– 6]. The standard explanation refers to an exotic component which has positive energy density and negative pressure, known as “dark energy” (DE). A variety of theoretical models has been proposed to explain this acceleration. The most natural and simplest model for DE is the ΛCDM model, containing a mixture of cosmological constant Λ and cold dark matter (CDM), for which the equation of state parameter is ω = −1 [7–9]. However, this model suffers from two major problems, namely, fine-tuning and cosmological coincidence problems [9–11]. In order to solve these problems, alternative DE models have been proposed, where the equation of state parameter evolves with cosmic time, mainly the canonical scalar field DE models [7,12–14] – see also [15,16] (for a historical review), which study the cosmological evolution with minimally coupled scalar fields. Another possibility is to consider non-canonical scalar field models, which has shown increasing interest [17–22]. We pay special attention on the tachyonic fields, which emerged in the context of string theories [23–26], and have been intensively studied in cosmology
[18,27–30]. It is possible to have accelerated expansion of the universe during the late times for both choices, and we have searched for situations in which correspondences can be established from a modified potential function. The correspondence above referred has already been investigated for defect structures, describing different scalar field theories with very similar properties [31–38]. The same idea was applied in the context of Friedmann–Robertson– Walker (FRW) cosmology [39], in a previous paper. In the present work, we extend this view and consider some popular DE parametrizations for canonical and tachyonic scalar field models. We find that the two models present the very same acceleration parameter, with the same energy density, and we name them twinlike models. The canonical potential and the tachyonic potential are distinct, but they lead to the same cosmological evolution. Our motivation f
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