Related papers: Adiabatic and entropy perturbations from inflation
We study the dynamics of inflation driven by an adiabatic self-gravitating medium, extending the previous works on fluid and solid inflation. Such a class of media comprises perfect fluids, zero and finite temperature solids. By using an…
In this article we investigate dependency of the adiabatic and entropy spectral indices of the cosmological perturbations on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e.…
Currently there is no definitive description for the accelerated expansion of the Universe at both early and late times; we know these two periods as the epochs of inflation and dark energy. Contained within this Thesis are two studies of…
We present a new general mechanism for generating curvature perturbations after inflation. Our model is based on the simple assumption that a field that starts to oscillate after inflation has a potential characterized by an underlying…
We provide an analytical study of the coupling of short and long wavelength fluctuation modes during the initial phase of reheating in two field models like hybrid inflation. In these models, there is - at linear order in perturbation…
We study the adiabatic density perturbation in the {\it oscillating inflation}, proposed by Damour and Mukhanov. The recent study of the cosmological perturbation during reheating shows that the adiabatic fluctuation behaves like as the…
We study primordial perturbations in Higgs--$R^2$ inflation in the presence of non-minimal kinetic mixing between the Higgs field and the scalaron. By numerically solving the multifield background and linear perturbation equations, we…
We study primordial perturbations from hyperinflation, proposed recently and based on a hyperbolic field-space. In the previous work, it was shown that the field-space angular momentum supported by the negative curvature modifies the…
We consider the non-commutative inflation model of [3] in which it is the unconventional dispersion relation for regular radiation which drives the accelerated expansion of space. In this model, we study the evolution of linear cosmological…
We consider a universe in which inflation commences because of a positive cosmological constant, the effect of which is progressively screened by the interaction between virtual gravitons that become trapped in the expansion of spacetime.…
We present a gauge-invariant formalism to study the evolution of curvature perturbations in a Friedmann-Robertson-Walker universe filled by multiple interacting fluids. We resolve arbitrary perturbations into adiabatic and entropy…
The evolution of the curvature perturbation after multi-field inflation is studied in the light of the curvaton mechanism. Past numerical studies show that many-field inflation causes significant evolution of the curvature perturbation…
This study presents a computational and theoretical framework inspired by thermodynamic principles to analyze the dynamics of economic inflation within adiabatic and non-adiabatic systems. In a framework referred to as developmental…
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…
We examine the processes of quantum squeezing and decoherence of density perturbations produced during a slowly contracting ekpyrotic phase in which entropic perturbations are converted to curvature perturbations before the bounce to an…
In cascade inflation and some other string inflation models, collisions of mobile branes with other branes or orbifold planes occur and lead to interesting cosmological signatures. The fundamental M/string-theory description of these…
We investigate whether non-adiabatic perturbations from inflation could produce an asymmetric distribution of temperature anisotropies on large angular scales in the cosmic microwave background (CMB). We use a generalised non-linear $\delta…
We study the non-gaussianity from the bispectrum in multi-field inflation models with a general kinetic term. The models include the multi-field K-inflation and the multi-field Dirac-Born-Infeld (DBI) inflation as special cases. We find…
We revisit a two-component inflaton model with a turning trajectory in the field space, where the field slowly rolls down along the trajectory. We consider the case when the effective mass in the direction perpendicular to the trajectory,…
We develop a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The…