Abstract
A nonsingular emergent universe cosmology can be realized by a nonconventional spinor field as first developed in [1]. We study the mechanisms of generating scale-invariant primordial power spectrum of curvature perturbation in the frame of spinor emergent universe cosmology. Particularly, we introduce a light scalar field of which the kinetic term couples to the bilinear of the spinor field. This kinetic coupling can give rise to an effective “Hubble radius” for primordial fluctuations which allows the scalar field to become squeezed at large length scales and to form a nearly scale-invariant power spectrum. We study the stability of the backreaction and constrain the forms of the coupling terms. Through a generalized curvaton mechanism, these almost scale-independent fluctuations are able to be transferred into curvature perturbation after the epoch of emergence and can thus explain cosmological observations.
Highlights
Inflation has become the most prevailing and successful model of describing physics of very early universe [2]
Inflationary cosmology has predicted a nearly scale-invariant power spectrum of primordial curvature perturbation which was confirmed by a series of Cosmic Microwave Background (CMB) observations [4]
It was pointed out in [5] that inflationary cosmology still suffers from the problem of the big bang singularity where conventional knowledge about mathematics and fundamental physics does not apply
Summary
Inflation has become the most prevailing and successful model of describing physics of very early universe [2] ( see [3] for early works). Inflationary cosmology has predicted a nearly scale-invariant power spectrum of primordial curvature perturbation which was confirmed by a series of Cosmic Microwave Background (CMB) observations [4] It was pointed out in [5] that inflationary cosmology still suffers from the problem of the big bang singularity where conventional knowledge about mathematics and fundamental physics does not apply. In this paper we study the possibility of generating a nearly scale-invariant primordial power spectrum in the model of spinor emergent universe. Depending on the detailed forms of the kinetic coupling, the curvaton field could feel it is in a “de-Sitter”-like background or a “matter-contraction”-like one In both two situations, a nearly scale-invariant power spectrum of isocurvature perturbations can form.
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