On finite time singularities in scalar field dark energy models based in the RS-II Braneworld

TL;DR

This paper investigates the occurrence of finite time singularities in scalar field dark energy models within RS-II Braneworld cosmology, using dynamical systems analysis and physical considerations, revealing possible weak and strong singularities.

Contribution

It provides a general analysis of singularities in RS-II Braneworld scalar field dark energy models without restricting potential forms or parameters, employing the Goriely-Hyde method and physical insights.

Findings

Finite time singularities can occur for specific initial conditions.

Models can exhibit weak singularities like Type III and IV.

Models can also lead to strong singularities such as the Big Rip.

Abstract

The quest of deciphering the true nature of dark energy has proven to be one of the most exciting in recent times in cosmology. Various ideas have been put forward in this regard besides the usual cosmological constant approach, ranging from scalar field based models like Quintessence and Phantom dark energy to various modified gravity approaches as well. A very interesting idea then is to consider scalar field dark energy models in quantum gravitationally corrected cosmologies with the RS-II Braneworld being one of the most well known in this regard. So in this work, we consider RS-II Braneworld based scalar field dark energy models and try to look out for the existence of finite time singularities in these regimes both through a dynamical system perspective, for which we employ the Goriely-Hyde singularity analysis method, and a physical perspective. Our approach is general in the sense that it is not limited to any particular class of potentials or for any constrained parameter region for the brane tension and is valid for both Quintessence and phantom dark energy regimes. We firstly show through Goriely-Hyde procedure that finite time singularities can exist in these models for a limited set of initial conditions and that this result would hold irrespective of any consideration given to the swampland dS conjecture. We then discuss the physical nature of the singularities that can occur in this regime, where we use a well motivated ansatz for the Hubble parameter and show that these models of dark energy can allow for weak singularities like those of Type III and Type IV and can also allow for strong singularities like the Big Rip (Type I).