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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/180421
Bouncing universes and dark energy
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Abstract
We consider the possibility of a universe whose dark energy (DE) is made out of a negative cosmological constant Λ and a dynamical component X, dubbed as ”cosmon”, which does not interact with Λ. Due to Λ < 0, the late-time accelerated expansion rate is caused by X. In this paper, the study of this framework has been performed by implementing a piece-wise function for the equation of state (EoS) parameter of the cosmon. This parametrization provides an analysis of the impact on the total DE behaviour when a transition from phantom-like to quintessence cosmon (or vice versa) takes place. It has been found that a stopping point in the Universe is displayed in the future when a transition of X from phantom-like to quintessence occurs. For such transition, the ratio of the DE density to matter density (ρD/ρm) is bounded, giving a possible solution to the cosmological coincidence problem. Furthermore, for a phantom-like cosmon at present, we can obtain values of the Hubble constant (H0) compatible with the ones acquired experimentally for cosmic microwave background data [1] and local data [2].
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Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutor: Joan Solà Peracaula
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SÁNCHEZ ALCALDE, Guillem. Bouncing universes and dark energy. [consulted: 21 of May of 2026]. Available at: https://hdl.handle.net/2445/180421