Hessence: A New View of Quintom Dark Energy

TL;DR

This paper introduces 'hessence', a novel non-canonical complex scalar field model for dark energy that enables crossing the phantom divide, unifying features of quintom models with improved stability and late-time behavior.

Contribution

It proposes a single-field 'hessence' model for dark energy that mimics quintom behavior and avoids issues like Q-ball formation, offering a new approach to crossing the phantom divide.

Findings

Hessence can realize crossing the phantom divide with a single field.

The model avoids Q-ball formation problems of previous complex scalar field models.

Proper potential choices make hessence behave like a Chaplygin gas at late times.

Abstract

Recently a lot of attention has been drawn to build dark energy model in which the equation-of-state parameter $w$ can cross the phantom divide $w=-1$. One of models to realize crossing the phantom divide is called quintom model, in which two real scalar fields appears, one is a normal scalar field and the other is a phantom-type scalar field. In this paper we propose a non-canonical complex scalar field as the dark energy, which we dub ``hessence'', to implement crossing the phantom divide, in a similar sense as the quintom dark energy model. In the hessence model, the dark energy is described by a single field with an internal degree of freedom rather than two independent real scalar fields. However, the hessence is different from an ordinary complex scalar field, we show that the hessence can avoid the difficulty of the Q-balls formation which gives trouble to the spintessence model (An ordinary complex scalar field acts as the dark energy). Furthermore, we find that, by choosing a proper potential, the hessence could correspond to a Chaplygin gas at late times.