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A new family of inflation models is introduced and studied. The models are characterised by a scalar potential which, far from the origin, approximates an inflationary plateau, while near the origin becomes monomial, as in chaotic…
We discuss bispectra of single-field inflationary models described by general Lorentz invariant Lagrangians that are at most first order in field derivatives, including the fast-roll models investigated by Noller and Magueijo. Based on a…
New exact inflationary solutions are presented in the scalar field theory, minimally coupled to gravity, with a potential term. No use is made of the slow rollover approximation. The scale factors are completely nonsingular and the…
It is shown in this letter that in the framework of an inhomogeneous geometry and a massive non self-interacting scalar field with spherical symmetry, one needs a homogeneous patch bigger than a dizaine of horizons in order to start…
In this work we study slow-roll inflation for a vector-tensor model with massive vector fields non-minimally coupled to gravity. The model under consideration has arbitrary parameters for each geometrical coupling. Taking into account a…
We consider tachyon condensation between a D-brane and an anti-D-brane in superstring theory, when they are separated in their common transverse directions. A simple rolling tachyon solution, that describes the time evolution of the…
Toy models for the Hubble rate or the scalar field potential have been used to analyze the amplification of scalar perturbations through a smooth transition from inflation to the radiation era. We use a Hubble rate that arises consistently…
We present our recent work on brane world models with a non-minimally coupled scalar field. In [9] we examined the stability of these models against scalar field perturbations and we discussed possible physical implications, while in [10]…
In this paper, we study inflation with {\alpha}-attractor potential in the RS braneworlds where high energy corrections to the Friedmann equation facilitate slow roll. In this scenario, we numerically investigate the inflationary parameters…
The main properties of the logamediate inflation driven by a non-canonical scalar field in the framework of DGP braneworld gravity are investigated. Considering high energy conditions we calculate the slow-roll parameters, analytically.…
At energies higher than the brane tension, the dynamics of a scalar field rolling down a potential are modified relative to the predictions of General Relativity. The modifications imply, among other things, that steeper potentials can be…
Using $\delta N$ formalism, in the context of a generic multi-field inflation driven on a non-flat field space background, we revisit the analytic expressions of the various cosmological observables such as scalar/tensor power spectra,…
We explore inflationary cosmology in a theory where there are two scalar fields which non-minimally couple to the Ricci scalar and an additional $R^2$ term, which breaks the conformal invariance. Particularly, we investigate the slow-roll…
We study the possibility that the approximate time shift symmetry during inflation is promoted to the full invariance under time reparametrization t \to \tilde t(t), or equivalently under field redefinition of the inflaton \phi \to…
Non-commutativity of spacetime at the Planck scale may deform the usual dispersion relations. And these deformed dispersion relations could lead to the accelerating phase without a scalar field. In this paper, we have calculated the…
In the literature, many warm inflationary models are formulated. In this piece of work, a warm inflationary model in the braneworld scenario is studied, considering constant and variable dissipation coefficients. Performance of the model…
Using only general properties of the tachyon potential we show that inflation may be generic when many branes and anti-branes become coincident. Inflation may occur because of: (1) the assistance of the many diagonal tachyon fields; (2)…
The slow roll approximation is studied for cosmological models in Hyperextended Scalar-Tensor Theories of Gravity. A procedure to obtain slow roll solutions in non-minimally coupled gravity is outlined and some examples are provided. An…
Upper bounds on the energy scale at the end of inflation in the Randall-Sundrum type II braneworld scenario are derived. The analysis is made exact by introducing new parameters that represent extensions of the Hubble flow parameters. Only…
The principles of a previously developed formalism for the covariant treatment of multi-scalar fields for which (as in a nonlinear sigma model) the relevant target space is not of affine type -- but curved -- are recapitulated. Their…