Related papers: Dirac-Born-Infeld and k-inflation: the CMB anisotr…
We show how observations of the perturbation spectra produced during inflation may be used to constrain the parameters of general scalar-tensor theories of gravity, which include both an inflaton and dilaton field. An interesting feature of…
Considerable and ongoing effort is made to identify promising scalar field candidates in string theory to drive a cosmological period of inflation. At stake is the possibility that fundamental string parameters could be encoded in…
We point out that if quantum field renormalization is taken into account, and the counterterms are evaluated at the Hubble-radius crossing time or few e-foldings after it, the predictions of slow-roll inflation for both the scalar and…
An alternative to the standard cold dark matter model has been recently proposed in which a significant fraction of the energy density of the universe is due to a dynamical scalar field ($Q$) whose effective equation-of-state differs from…
We study models of modular inflation of the form expected to arise from low energy effective actions of superstring theories. We argue on general grounds that the most likely models of modular slow-roll inflation are small field models in…
We consider non-minimally coupled (with gravity) scalar field with non-canonical kinetic energy. The form of the kinetic term is of Dirac-Born-Infeld (DBI) form.We study the early evolution of the universe when it is sourced only by the…
Space-based missions studying the cosmic microwave background (CMB) have progressively refined the parameter space in conventional models of inflation shortly ($\sim 10^{-37}$ seconds) after the big bang. While most inflationary scenarios…
Using the constant-roll approach, DBI inflationary scenario will be studied and it is sought to compare the result with observational data. By considering the cosmological perturbations of the model, it is realized that some extra terms…
There is solid theoretical and observational motivation behind the idea of scale-invariance as a fundamental symmetry of Nature. We consider a recently proposed classically scale-invariant inflationary model, quadratic in curvature and…
Inflation in a five-dimensional brane world model with two boundary branes is studied. We make use of the moduli space approximation whereby the low energy theory reduces to a four-dimensional biscalar-tensor gravity plus a minimally…
In the previous work, a new kind of inflation model was proposed, which has the interesting property that its perturbation equation of motion gets a correction of k^4, due to the non-linearity of the kinetic term. Nonetheless, the…
This work investigates a single-field inflationary model, a specific class of the K-essence models where a coupling term exists between canonical Lagrangian and the potential. This coupling term has many effects on key inflationary…
Recently, we have shown that scalar spectra with lower power on large scales and certain other features naturally occur in {\it punctuated inflation}, i.e. the scenario wherein a brief period of rapid roll is sandwiched between two stages…
We study the CMB observables in axion monodromy inflation. These well-motivated scenarios for inflation in string theory have monomial potentials over super-Planckian field ranges, with superimposed sinusoidal modulations from instanton…
Constant-roll inflation was recently introduced by Motohashi, Starobinsky and Yokoyama as a phenomenological way to parametrize deviations from the slow-roll scenarios. In this paper, we investigate the dynamics of both the background and…
We study inflection point inflation using Singularity Theory, which relates degenerate critical points of functions to their local behavior. This approach illuminates universal features of small-field models and gives analytic control over…
We argue that the non-detection of primordial tensor modes has taught us a great deal about the primordial universe. In single-field slow-roll inflation, the current upper bound on the tensor-to-scalar ratio, $r < 0.07$ $(95 \% ~CL)$,…
We revisit the issue on signatures of pre-inflationary background anisotropy by considering the quantization of a massless and minimally coupled scalar field in an axially symmetric Kasner background, mimicking cosmological perturbations.…
Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy…
We investigate the scalar perturbation of the inflation model driven by a massive-scalar field in Eddington-inspired Born-Infeld gravity. We focus on the perturbation at the attractor stage in which the first and the second slow-roll…