Abstract
We study an inflationary scenario where thermal inflation is followed by fast-roll inflation. This is a rather generic possibility based on the effective potentials of spontaneous symmetry breaking in the context of particle physics models. We show that a large enough expansion could be achieved to solve cosmological problems. However, the power spectrum of primordial density perturbations from the quantum fluctuations in the inflaton field is not scale invariant and thus inconsistent with observations. Using the curvaton mechanism instead, we can obtain a nearly scale invariant spectrum, provided that the inflationary energy scale is sufficiently low to have long enough fast-roll inflation to dilute the perturbations produced by the inflaton fluctuations.
Highlights
Inflation [1] is considered to be the most promising candidate to provide the initial conditions for the successful hot big bang theory, solving many cosmological problems such as homogeneity, isotropy and flatness of the observable universe
The most pristine form of these perturbations is inscribed as the temperature anisotropy in the cosmic microwave background (CMB), which was first probed by the Cosmic Background Explorer (COBE) satellite [2]
One obvious difficulty is that it is not easy to achieve the slow-roll conditions in the context of particle physics models, e.g., in supergravity theories. This makes the total expansion of the universe during the stage of inflation very short and the spectrum of density perturbations produced during inflation highly scale dependent
Summary
Inflation [1] is considered to be the most promising candidate to provide the initial conditions for the successful hot big bang theory, solving many cosmological problems such as homogeneity, isotropy and flatness of the observable universe. The paradigm of slow-roll inflation [7] is a very useful and attractive principle to discriminate which model is able to implement long enough inflation for homogeneous and flat universe and to generate an almost scale invariant spectrum of density perturbations. We can expect that the energy scale associated with the last inflationary stage is considerably low compared with the Planck scale This is motivated by the inflation models based on the de Sitter vacua construction by string moduli stabilisation [9], where the Hubble parameter H cannot be greater than gravitino mass m3/2 [10] which is of O(TeV) in phenomenologically interesting gravity mediated supersymmetry breaking case.
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