Constraints on Chiral-Quintom dark energy after DESI DR2 and impact on unifying dark energy with inflation

TL;DR

This paper investigates a two-scalar field Chiral-Quintom model that unifies early inflation and late dark energy, constrained by recent DESI DR2 data, and compares its performance with standard cosmological models.

Contribution

It introduces a novel two-field Chiral-Quintom framework capable of unifying inflation and dark energy, and assesses its viability using recent observational data.

Findings

The model can cross the phantom divide without instabilities.

It fits observational data comparably to ΛCDM and w0waCDM models.

Multiple-field dynamics are not ruled out by current data.

Abstract

The recent data release DR2 from the Dark Energy Spectroscopic Instrument (DESI) has reinforced compelling evidence supporting the dynamical nature of dark energy. In this respect, we here explore a two-scalar field cosmological model, dubbed Chiral-Quintom paradigm, that allows for a unified description of early- and late-time cosmic accelerations, namely inflation and dark energy, respectively. Moreover, we show that it provides a mechanism to cross the phantom divide without instabilities. To do so, we first focus on scenarios where the scalar fields evolve under an exponential potential, leading to distinct cosmological behaviors, including tracking solutions and slow-roll or hyperbolic inflation. Afterwards, by considering a nonlinear potential and a mixing in the kinetic sector, we show that the model can also describe the matter-dominated era, offering a potential unification of the dark sector. Accordingly, we place bounds on this double-field paradigm by employing recent low-redshift observational data, including supernovae from the Pantheon+ and Union3.0 compilations, observational Hubble parameter measurements, and baryon acoustic oscillation data from the latest DESI release. By means of the Akaike information criterion, the standard $\Lambda$CDM scenario and the $w_0w_a$CDM model are thus compared with the Chiral-Quintom approach, showing that, in principle, multiple-field dynamics does not seem to be ruled out, ultimately providing a flexible framework for describing late-time dynamics.