Related papers: A two-scalar model for a small but nonzero cosmolo…
Within the holographic cosmology paradigm, specifically the model of McFadden and Skenderis, but more generally than that, the cosmological constant is found to naturally flow from a large value, to a small value, which can even be as low…
Cosmic inflation is one of the most important paradigms in modern cosmology. In its simplest form, inflation is driven by a single inflaton field. However, multi-field inflation has become increasingly attractive because it can solve many…
We study a scale-invariant model of quadratic gravity with a non-minimally coupled scalar field. We focus on cosmological solutions and find that scale invariance is spontaneously broken and a mass scale naturally emerges. Before the…
We investigate a very general class of cosmological models with scalar fields non-minimally coupled to gravity. A particular representative in this class is given by the non-minimal Higgs inflation model in which the Standard Model Higgs…
We investigate a conformal invariant gravitational model which is taken to hold at pre-inflationary era. The conformal invariance allows to make a dynamical distinction between the two unit systems (or conformal frames) usually used in…
A survey of solutions to the cosmological moduli problem in string theory. The only extant proposal which may work is Intermediate Scale Inflation as proposed by Randall and Thomas. Supersymmetry preserving dynamics which could give large…
We point out that a light scalaron dynamically emerges if scalar fields have a sizable non-minimal coupling to the Ricci scalar as in the Higgs inflation model. We support this claim in two ways. One is based on the renormalization group…
Cosmological models with inflation and those with bounce have their own strengths and weaknesses. Here we construct a model in which a phase of bounce is followed by a viable inflationary phase. This incorporates several advantages of both…
In construction of an inflationary model, one usually assumes that the matter sector of the gravitational action is minimally coupled to the background. It means that the matter (inflaton) part of the action is coupled with the same metric…
Current astronomical observations are successfully explained by the present cosmological paradigm based on the concordance model ($\Lambda_0$CDM + Inflation). However, such a scenario is composed of a heterogeneous mix of ingredients for…
An exact scalar field cosmological model is constructed from the exact solution of the field equations. The solutions are exact and no approximation like slow roll is used. The model gives inflation, solves horizon and flatness problems.…
We show that it is possible to combine an early phase of String Gas Cosmology which can explain the origin of the observed structures on cosmological scales with a short later period of power law inflation which creates spatial flatness.…
The cosmological solutions of the non-minimal $ Y (R)F^2 $ theory which are compatible with FRW space-time are investigated. In order to avoid the isotropy violation of a vector field, it can be considered that the presence of a triplet of…
There exists a growing body of observational evidence supporting a non-vanishing cosmological constant at the present epoch. We examine the possibility that such a term may arise directly from the potential energy which drove an…
We study a model of inflation where the scalar perturbations are almost gaussian while there is sizable (equilateral) nongaussianity in the tensor sector. In this model, a rolling pseudoscalar gravitationally coupled to the inflaton…
A simple model is introduced in which the cosmological constant is interpreted as a true Casimir effect on a scalar field filling the universe (e.g. $\mathbf{R} \times \mathbf{T}^p\times \mathbf{T}^q$, $\mathbf{R} \times \mathbf{T}^p\times…
We derive a Higgs inflationary model in the context of holographic cosmology, where we consider a universe filled with a Higgs field non-minimally coupled to gravity in a slow-roll regime. The amplitude of density (scalar) perturbations is…
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…
We study adiabatic and isocurvature perturbation spectra produced by a period of cosmological inflation driven by two scalar fields. We show that there exists a model-independent consistency condition for all two-field models of slow-roll…
The nonminimal coupling (NMC) of the scalar field to the Ricci curvature is unavoidable in many cosmological scenarios. Inflation and quintessence models based on nonminimally coupled scalar fields are studied, with particular attention to…