Related papers: Late Inflation and the Moduli Problem of Sub-Milli…
We study the supergravity hybrid inflation model of Ref.[1] in the presence of a modulus field. The eta-problem is solved by a shift symmetry for the inflaton, which protects the inflaton mass even in the presence of the modulus field.…
A radiative seesaw model with an inert doublet dark matter is a promising candidate which could explain the existence of neutrino masses, dark matter and baryon number asymmetry of the Universe, simultaneously. In addition to these issues,…
We study the problem of scalar particle production after inflation by a rapidly oscillating inflaton field. We use the framework of the chaotic inflation scenario with quartic and quadratic inflaton potentials. Particular attention is paid…
Cosmological inflation is studied in the case where the inflaton is the overall modulus $T$ for an orbifold. General forms of the (non-perturbative) superpotential are considered to ensure that $G=K+{\rm ln}|W|^2$ is modular invariant. We…
String theory abounds with light scalar fields (the dilaton and various moduli) which create a host of observational problems, and notably some serious cosmological difficulties similar to the ones associated with the Polonyi field in the…
Ignorance of the initial condition for the axion dynamics in the early Universe has led us to consider an $O(1)$ valued initial amplitude, and that prefers the decay constant, $F_a$, of the QCD axion to be an intermediate scale such as…
The radiative neutrino mass model with inert doublet dark matter is a promising model for the present experimental issues which cannot be explained within the standard model. We study an extension of this model focusing on cosmological…
Many models of supersymmetry breaking involve particles with weak scale mass and Planck mass suppressed couplings. Coherent production of such particles in the early universe destroys the successful predictions of nucleosynthesis. We show…
We investigate moduli field dynamics in supergravity/M-theory like set ups where we turn on fluxes along some or all of the extra dimensions. As has been argued in the context of string theory, we observe that the fluxes tend to stabilize…
An epoch of accelerated expansion, or inflation, in the early universe solves several cosmological problems. While there are many models of inflation only recently has it become possible to discriminate between some of the models using…
Within the framework of a five-dimensional brane world with a stabilized radion, we compute the cosmological perturbations generated during inflation and show that the perturbations are a powerful tool to probe the physics of extra…
Dark matter and cosmic inflation represent two of the major puzzles in cosmology. They are typically addressed by introducing separate fields with independent dynamics. On the other hand, extra dimensions might play an important role for…
We estimate the abundance of the coherent oscillation of moduli, which linearly couple to matter fields through higher dimensional operators. During the (p)reheating after inflation, matter particles are efficiently produced and it can…
The early Universe inflation is well known as a promising theory to explain the origin of large scale structure of Universe and to solve the early universe pressing problems. For a resonable inflation model, the potential during inflation…
We present a model where the inflaton can naturally account for all the dark matter in the Universe within the warm inflation paradigm. In particular, we show that the symmetries of the Warm Little Inflaton scenario (i) avoid large thermal…
We investigate the nonlinear dynamics of hybrid inflation models, which are characterized by two real scalar fields interacting quadratically. We start by solving numerically the coupled Klein-Gordon equations in static Minkowski spacetime,…
We analyze the evolution of the perturbations in the inflaton field and metric following the end of inflation. We present accurate analytic approximations for the perturbations, showing that the coherent oscillations of the…
We investigate the possibility of obtaining inflationary solutions of the slow roll type from a low energy Lagrangian coming from superstrings. The advantage of such an approach is that in these theories the scalar potential has only one…
The inflationary phase of the Universe is explored by proposing a toy model related to the scalar field, termed as {\it inflaton}. The potential part of the energy density in the said era is assumed to have a constant vacuum energy density…
The basic properties of oscillons -- localized, long-lived, time-dependent scalar field configurations -- are briefly reviewed, including recent results demonstrating how their existence depends on the dimensionality of spacetime. Their…