Related papers: Multidimensional gravity with higher derivatives a…
We generalize the known equivalence between higher order gravity theories and scalar tensor theories to a new class of theories. Specifically, in the context of a first order or Palatini variational principle where the metric and connection…
We consider an inflection point inflationary model in supergravity with a single chiral superfield and show that the predicted values of the scalar spectral index and tensor-to-scalar ratio are consistent with the Planck 2015 results. In…
We study multifield inflation in scenarios where the fields are coupled non-minimally to gravity via $\xi_I(\phi^I)^n g^{\mu\nu}R_{\mu\nu}$, where $\xi_I$ are coupling constants, $\phi^I$ the fields driving inflation, $g_{\mu\nu}$ the…
We perform a general study of the primordial scalar non-Gaussianities in multi-field inflationary models in Einstein gravity. We consider models governed by a Lagrangian which is a general function of the scalar fields and their first…
Very few explicit inflationary scenarios are known to generate a large bispectrum of orthogonal shape. Dirac-Born-Infeld Galileon inflation, in which an induced gravity term is added to the DBI action, is one such model. We formulate it in…
We consider an alternative higher order gravity theory which is non-analytic in the Ricci curvature. It has power-law inflationary behaviour. This is further evidence that inflation is a general property of higher derivative gravity…
We explore a new possibility that some inflaton fields in multi-field inflation models satisfy the observed value of the spectral index so that the curvature perturbation generated by them through post-inflationary dynamics may be relevant…
A scalar potential obtained from the $D$-term in the Supergravity models, which dominates over $F$ term and is mainly responsible for the inflationary phase in the early universe, is studied. The potential with canonical kinetic terms for…
In this paper, we investigate models where a scalar field driving inflation is minimally coupled with gravity and it is subjected to a scalar potential. We present several examples of coupling between the field and gravity, and we furnish…
Quintessential inflation utilises a single scalar field to account for the observations of both cosmic inflation and dark energy. The requirements for modelling quintessential inflation are described and two explicit successful models are…
An alternative scenario about the phenomenology of primordial Universe is k-inflation. According to this concept, inflation can be achieved by nonstandard kinetic term of scalar field, namely the inflaton. In this project we focus on…
We show that there are inflationary models for which perturbations in the energy momentum tensor, which are of second order in the scalar field, cannot be neglected. We first specify the conditions under which the usual first order…
We study models where a scalar field has derivative and non-derivative couplings to the Ricci tensor and the co-Ricci tensor with a view to inflation. We consider both the metric formulation and the Palatini formulation. In the Palatini…
One of the fundamental objectives of contemporary cosmology is to understand the physics of the inflationary universe, owing to its observably verifiable predictions about the very early universe with an energy scale of $\sim 10^{16}$ GeV.…
We study the linear perturbations of multi-field inflationary models governed by a Lagrangian which is a general function of the scalar fields and of a global kinetic term combining their spacetime gradients with an arbitrary field space…
We discuss inflation in models with large extra dimensions, driven by a bulk scalar field. The brane inflaton is then a single effective field, obtained from the bulk scalar field by scaling. The self interaction terms of the effective…
We examine an inflationary model in $R + R^2$ gravity with torsion, where $R^2$ denotes five independent quadratic curvature invariants; it turns out that only two free parameters remain in this model. We show that the behavior of the scale…
Within the framework of metric-affine theories of gravity, where both the metric and connection are treated as independent variables, we consider actions quadratic in the Ricci scalar curvature coupled non-minimally to a scalar field…
Predictions of inflationary schemes can be influenced by the presence of extra dimensions. This could be of particular relevance for the spectrum of gravitational waves in models where the extra dimensions provide a brane-world solution to…
We study inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan terms with the Higgs field non-minimally coupled to them leads to three additional coupling…