15,660 research outputs found
Aspects of warm-flat directions
Considering the mechanism of dissipative slow-roll that has been used in warm
inflation scenario, we show that dissipation may alter usual cosmological
scenarios associated with SUSY-flat directions. We mainly consider SUSY-flat
directions that have strong interactions with non-flat directions and may cause
strong dissipation both in thermal and non-thermal backgrounds. An example is
the Affleck-Dine mechanism in which dissipation may create significant (both
qualitative and quantitative) discrepancies between the conventional scenario
and the dissipative one. We also discuss several mechanisms of generating
curvature perturbations in which the dissipative field, which is distinguished
from the inflaton field, can be used as the source of cosmological
perturbations. Considering the Morikawa-Sasaki dissipative coefficient, the
damping caused by the dissipation may be significant for many MSSM flat
directions even if the dissipation is far from thermal equilibrium.Comment: 22 pages, accepted for publication in International Journal of Modern
Physics
Curvaton paradigm can accommodate multiple low inflation scales
Recent arguments show that some curvaton field may generate the cosmological
curvature perturbation. As the curvaton is independent of the inflaton field,
there is a hope that the fine-tunings of inflation models can be cured by the
curvaton scenario. More recently, however, D.H.Lyth discussed that there is a
strong bound for the Hubble parameter during inflation even if one assumes the
curvaton scenario. Although the most serious constraint was evaded, the bound
seems rather crucial for many models of a low inflation scale. In this paper we
try to remove this constraint. We show that the bound is drastically modified
if there were multiple stages of inflation.Comment: 9pages, no figure, references added, final versio
Elliptic Inflation: Generating the curvature perturbation without slow-roll
There are many inflationary models in which inflaton field does not satisfy
the slow-roll condition. However, in such models, it is always difficult to
generate the curvature perturbation during inflation. Thus, to generate the
curvature perturbation, one must introduce another component to the theory. To
cite a case, curvatons may generate dominant part of the curvature perturbation
after inflation. However, we have a question whether it is unrealistic to
consider the generation of the curvature perturbation during inflation without
slow-roll. Assuming multi-field inflation, we encounter the generation of the
curvature perturbation during inflation without slow-roll. The potential along
equipotential surface is flat by definition and thus we do not have to worry
about symmetry. We also discuss about KKLT models, in which corrections lifting
the inflationary direction may not become a serious problem if there is a
symmetry enhancement at the tip (not at the moving brane) of the inflationary
throat.Comment: 27pages, 8figures, to appear in JCA
Can The Majorana neutrino CP-violating phases be restricted ?
We reanalyze the constraints in neutrino masses and MNS lepton mixing
parameters using the new data from the terrestrial (KamLAND) and astrophysical
(WMAP) observations together with the HEIDELBERG-MOSCOW double beta decay
experiment. It leads us to the almost degenerate or inverse hierarchy neutrino
mass scenario. We discuss the possibility of getting the bound for the Majorana
CP violating phase.Comment: 6 pages, 2 figure
Generating the curvature perturbation with instant preheating
A new mechanism for generating the curvature perturbation at the end of
inflaton has been investigated. The dominant contribution to the primordial
curvature perturbation may be generated during the period of instant
preheating. The mechanism converts isocurvature perturbation related to a light
field into curvature perturbation, where the ``light field'' is not the
inflaton field. This mechanism is important in inflationary models where
kinetic energy is significant at the end of inflaton. We show how one can apply
this mechanism to various brane inflationary models.Comment: 17 pages, 1 figure, To appear in JCA
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