New Scalar Field Quartessence

TL;DR

This paper introduces a scalar field model where a single field accounts for both Dark Matter and Dark Energy, with dynamics depending on redshift and structure formation, providing a unified cosmological scenario.

Contribution

It presents a novel scalar field framework that unifies Dark Matter and Dark Energy through redshift-dependent trapping and rolling mechanisms.

Findings

Scalar field acts as Dark Matter at high redshift

Field transitions to Dark Energy at low redshift

Model explains coexistence of Dark Matter and Dark Energy

Abstract

We propose a cosmological scenario involving a scalar field, $\varphi$, that is a source of Dark Matter as well as of Dark Energy. Besides $\varphi$, the Lagrangian of the field theory envisaged in our scenario contains a second field $\chi$, for simplicity assumed to be a scalar, too. For fixed values of $\chi$, the potential term decays exponentially at large positive values of $\varphi$. While $\varphi$ is not coupled to Standard Model fields, $\chi$ is assumed to be coupled to them, and the Green functions of $\chi$ depend on the cosmological redshift in the expanding universe. We assume that the term in the Lagrangian coupling $\chi$ to $\varphi$ is such that, at redshifts $z$ larger than some critical redshift $z_c$, $\varphi$ is trapped near $\varphi=0$, and oscillations of $\varphi$ about $\varphi=0$ describing massive scalar particles give rise to Dark Matter. At redshifts below $z_c$, the field $\varphi$ is no longer trapped near the origin and starts to `roll' towards large field values. A homogenous component of $\varphi$ emerges that acts as Dark Energy. Within over-dense regions, such as galaxies and galaxy clusters, the redshifting of $\chi$ stops, and $\varphi$ therefore remains trapped near $\varphi=0$ as long as $z_c$ is smaller than the redshift when structures on galactic scales decouple from the Hubble flow. Thus, at the present time, $\varphi$ describes both Dark Energy and Dark Matter.