147 research outputs found
Modular thermal inflation without slow-roll approximation
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.Comment: (v1) 13 pages, 1 table, no figure; (v2) 14 pages, 1 table, no figure,
References added; (v3) A new subsection (3.2.3) added, one reference added,
to appear in Physics Letters
Exact Analytic Solution for Non-Linear Density Fluctuation in a LCDM Universe
We derive the exact third-order analytic solution of the matter density
fluctuation in the proper-time hypersurface in a CDM universe,
accounting for the explicit time-dependence and clarifying the relation to the
initial condition. Furthermore, we compare our analytic solution to the
previous calculation in the comoving gauge, and to the standard Newtonian
perturbation theory by providing Fourier kernels for the relativistic effects.
Our results provide an essential ingredient for a complete description of
galaxy bias in the relativistic context.Comment: 20 pages, no figures, published in JCA
A new parameter in attractor single-field inflation
We revisit the notion of slow-roll in the context of general single-field
inflation. As a generalization of slow-roll dynamics, we consider an inflaton
in an attractor phase where the time derivative of is determined
by a function of , . In other words, we consider
the case when the number of -folds counted backward in time from the end
of inflation is solely a function of , . In this case, it is
found that we need a new independent parameter to properly describe the
dynamics of the inflaton field in general, in addition to the standard
parameters conventionally denoted by , , and . Two
illustrative examples are presented to discuss the non-slow-roll dynamics of
the inflaton field consistent with observations.Comment: (v1) 11 pages; (v2) 12 pages, discussions improved including the
running, to appear in Physics Letters
Towards general patterns of features in multi-field inflation
We investigate the consequences of general curved trajectories in multi-field
inflation. After setting up a completely general formalism using the mass
basis, which naturally accommodates the notion of light and heavy modes, we
study in detail the simple case of two successive turns in two-field system. We
find the power spectrum of the curvature perturbation receives corrections that
exhibit oscillatory features sinusoidal in the logarithm of the comoving
wavenumber without slow-roll suppression. We show that this is because of the
resonance of the heavy modes inside and outside the mass horizon.Comment: (v1) 16 pages, 2 figures; (v2) 17 pages, minor updates, to appear in
Journal of High Energy Physic
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