Abstract
We consider a hybrid scalar field which is nonminimally coupled to the matter and models a chameleon cosmology. By introducing an effective potential, we study the dependence of the effective potential's minimum and hybrid chameleon field's masses on the local matter density. In a dynamical system technique, we analyze the phase space of this two-field chameleon model, find its fixed points and study their stability. We show that the hybrid chameleon domination solution is a stable attractor and the universe in this setup experiences a phantom divide crossing.
Highlights
Recent cosmological observations have revealed that our universe is currently undergoing an accelerating phase of expansion [1–14]
We have studied a hybrid chameleon model in detail
We have found that the minimum of the effective chameleon potential is a line and in order for this minimum to exist, there is a constraint on the parameters space of the model
Summary
Recent cosmological observations have revealed that our universe is currently undergoing an accelerating phase of expansion [1–14]. The standard cosmological model with a cosmological constant has no internal problems or inconsistencies both at the classical and quantum levels [42] In this regard, the scalar fields, such as quintessence [43, 44], phantom fields [45], and tachyon fields [46, 47] and so on, provide a simple dynamical model for dark energy which can explain cosmic accelerating expansion. On the cosmological scales, where the density is very low, the mass of the fields can be of the order of the present Hubble parameter (H0) and cause the current acceleration of the universe. Such a scalar field is dubbed “chameleon” because its physical properties, such as its mass, depend on its environment [56, 57]. By increment of the scalar fields, the runaway potential decreases, while the coupling term increases
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