# Inflation with 0 ≤ c s ≤ 1

@article{Gorji2022InflationW0, title={Inflation with 0 ≤ c s ≤ 1}, author={Mohammad Ali Gorji and Hayato Motohashi and Shinji Mukohyama}, journal={Journal of Cosmology and Astroparticle Physics}, year={2022}, volume={2022} }

We investigate a novel single field inflationary scenario which allows a transition between a slow-roll k-inflation with c s of order unity and a ghost inflation with c s ≃ 0, where c s is the sound speed for the curvature perturbations. We unify the two phases smoothly by appropriately taking into account a higher derivative scordatura term, which is always there from the effective field theory point of view but which becomes important only in the c s ≃ 0 regime. The model achieves the whole…

## 3 Citations

DBI inflation and warped black holes

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

We study a possible amplification mechanism for the curvature perturbations generated during inflation by a Dirac-Born-Infeld (DBI) inflaton in the presence of a sharp feature in the warp factor. The…

The effective field theory of vector-tensor theories

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

We investigate a systematic formulation of vector-tensor theories based on the effective field theory (EFT) approach. The input of our EFT is that the spacetime symmetry is spontaneously broken by…

Effective Field Theory of Black Hole Perturbations with Timelike Scalar Profile: Formulation

- Physics
- 2022

We formulate the Eﬀective Field Theory (EFT) of perturbations within scalar-tensor theories on an inhomogeneous background. The EFT is constructed while keeping a background of a scalar ﬁeld to be…

## References

SHOWING 1-10 OF 90 REFERENCES

Horizon crossing and inflation with large η

- Physics
- 2005

I examine the standard formalism of calculating curvature perturbations in inflation at horizon crossing, and derive a general relation which must be satisfied for the horizon-crossing formalism to…

Ghost Inflation

- Physics
- 2003

We propose a new scenario for early cosmology, where an inflationary de Sitter phase is obtained with a ghost condensate. The transition to radiation dominance is triggered by the ghost itself,…

Large power spectrum and primordial black holes in the effective theory of inflation

- PhysicsJournal of High Energy Physics
- 2022

We study the generation of a large power spectrum, necessary for primordial black hole formation, within the effective theory of single-field inflation. The mechanisms we consider include a…

DBI inflation and warped black holes

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

We study a possible amplification mechanism for the curvature perturbations generated during inflation by a Dirac-Born-Infeld (DBI) inflaton in the presence of a sharp feature in the warp factor. The…

Tilted ghost inflation

- Geology
- 2005

In a ghost inflationary scenario, we study the observational consequences of a tilt in the potential of the ghost condensate. We show how the presence of a tilt tends to make contact between the…

Relaxing the cosmological constant: a proof of concept

- Physics
- 2016

A bstractWe propose a technically natural scenario whereby an initially large cosmological constant (c.c.) is relaxed down to the observed value due to the dynamics of a scalar evolving on a very…

The Effective Field Theory of Inflation

- Physics
- 2008

We study the effective field theory of inflation, i.e. the most general theory describing the fluctuations around a quasi de Sitter background, in the case of single field models. The scalar mode can…

Ultra Slow-Roll Inflation and the non-Gaussianity Consistency Relation

- Computer Science
- 2013

It is demonstrated that the power spectrum remains scale-invariant and that the bi-spectrum is of the local type with fnl=5(3-ns)/4 which represents a modification of the consistency relation.