Hessence: a new view of quintom dark energy

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-ball 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. *

Quintom models with an equation of state crossing−1

“…These results are the same as with the conclusion in Ref. [17], where the authors found that the hessence models with exponential potentials have the stable attractor solutions with ! ÿ1 2 =3, and the models with power law potentials have the stable attractor solutions with !…”

“…0 Q Þ 0. We should notice that, in our discussion, we have not considered the possible interaction between the quintom field and the background matter, which may show some new interesting characters [17].…”

“…[17]. But it is clear that this form requires an additional requirement, (14) here the variables ( , ) are defined by…”

“…which is associated with the total conserved charge within the physical volume due to the internal symmetry [17], if one considers the hessence as a noncanonical complex scalar field. It turns out…”

Transition from quintessence to the phantom phase in the quintom model

“…In [17] the same calculation has been done by introducing an interaction term between phantom and quintessence fields. Recently, the hessence model, as a new view of quintom dark energy, in which the dark energy is described by a single non-canonical complex scalar field, rather than two independent real scalar fields, has been introduced [18]. The evolution of ω in this model has been studied in [19] and [20], via phase-space analysis.…”