Related papers: Gravitational Wave Constraints on DBI Inflation
Although inflationary models generically predict a flat spectrum of gravitational waves, we point out a general process that produces a sharply peaked spectrum of gravitational radiation. This process is generic for inflationary models with…
We consider an intermediate Dirac-Born-Infeld (DBI) inflationary model in the presence of a minimal measurable length in the theory. We show that, the presence of a minimal measurable length modifies the definitions of the scalar and tensor…
The curvaton scenario for the generation of the cosmological curvature perturbation on large scales represents an alternative to the standard slow-roll scenario of inflation in which the observed density perturbations are due to…
A plateau on the background inflaton potential $V_{\rm b}(\phi)$ can lead cosmic inflation into an ultraslow-roll phase, greatly enhancing the primordial power spectrum on small scales, and resulting in intensive scalar-induced…
We analyse the implications for inflationary models of the cosmic microwave background (cmb) anisotropy measured by COBE. Vacuum fluctuations during inflation generate an adiabatic density perturbation, and also gravitational waves. The…
The primordial spectrum of fluctuations may present a large peak as a result of enhancing features during inflation. This may include, but is not limited to, bumps in the inflaton's potential, phases of ultra-slow-roll or turns in…
With an energy scale that can be as high as $10^{14}\,{\rm GeV}$, inflation may provide a unique probe of high-energy physics. Both scalar and tensor fluctuations generated during this early accelerated expansion contain crucial information…
We discuss a cosmological scenario with a stochastic background of gravitational waves sourced by the tensor perturbation due to a hybrid inflationary model with cubic potential. The tensor-to-scalar ratio for the present hybrid…
We show that curvature perturbations acquire a scale invariant spectrum for any constant equation of state, provided the fluid has a suitably time-dependent sound speed. In order for modes to exit the physical horizon, and in order to solve…
Gravitational waves (GW) produced in the early Universe contribute to the number of relativistic degrees of freedom, $N_{\rm eff}$, during Big Bang Nucleosynthesis (BBN). By using the constraints on $N_{\rm eff}$, we present a new bound on…
At the linear level, the gravitational wave (GW) spectrum predicted by inflation, and many of its alternatives, can have arbitrarily small amplitude and consequently an unconstrained tilt. However, at second order, tensor fluctuations are…
The reheating phase after inflation is one of the least observationally constrained epochs in the evolution of the Universe. The forthcoming gravitational wave observatories will enable us to constrain at least some of the non-standard…
In this paper we examine the IR inflation scenario using the DBI action, where we have $N$ multiple branes located near the tip of a warped geometry. At large $N$ the solutions are similar in form to the more traditional single brane…
We give the initial spectrum of quantized gravitational waves in the context of the one-bubble open inflationary universe scenario. In determining the quantum state after the bubble nucleation we adopt the prescription to require the…
In this lecture I will review the present status of inflation within string-based brane-world scenarios. The idea is to start from a supersymmetric configuration with two parallel static Dp-branes, and slightly break the supersymmetry…
In scalar-tensor theories the scalar fields generically couple nontrivially to gravity. We study the observable properties of inflationary models with non-minimally coupled inflaton and Dirac-Born-Infeld (DBI) kinetic term. Within the…
We consider a scenario of cosmological inflation coming from a grand unified theory in higher dimensional orbifold. Flatness of the potential is automatically guaranteed in this orbifold setup thanks to the nonlocality of the Wilson line on…
Supersolid inflation is a class of inflationary theories that simultaneously breaks time and space reparameterization invariance during inflation, with distinctive features for the dynamics of cosmological fluctuations. We investigate…
We study the preheating process in a model of DBI inflation with a DBI-type inflaton coupling to a canonical entropy field. At the end of inflation, the inflaton field oscillates around its vacuum which can arise from an infrared cutoff…
We analyze the trajectories for multifield DBI inflation, which can arise in brane inflation models, and show that the trajectories are the same as in typical slow roll inflation. We calculate the power spectrum and find that the higher…