# Inflation with $0 \leq c_{\rm s} \leq 1$

@inproceedings{Gorji2021InflationW, title={Inflation with \$0 \leq c\_\{\rm s\} \leq 1\$}, author={Mohammad Ali Gorji and Hayato Motohashi and Shinji Mukohyama}, year={2021} }

We investigate a novel single field inflationary scenario which allows a transition between a slow-roll k-inflation with cs of order unity and a ghost inflation with cs ' 0, where cs 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 cs ' 0 regime. The model achieves the whole range…

## 4 Citations

### Growth of power spectrum due to decrease of sound speed during inflation

- PhysicsPhysical Review D
- 2022

We study the ampliﬁcation of the curvature perturbations due to a small sound speed and ﬁnd that its origin is diﬀerent completely from that due to the ultraslow-roll inﬂation. This is because when…

### Avoidance of Strong Coupling in General Relativity Solutions with a Timelike Scalar Profile in a Class of Ghost-Free Scalar-Tensor Theories.

- PhysicsPhysical review letters
- 2022

Modified gravity theories can accommodate exact solutions, for which the metric has the same form as the one in general relativity, i.e., stealth solutions. One problem with these stealth solutions…

### Generalized Regge-Wheeler equation from Effective Field Theory of black hole perturbations with a timelike scalar profile

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2022

Recently, the Effective Field Theory (EFT) of perturbations on an arbitrary background metric with a timelike scalar profile was formulated in the context of scalar-tensor theories. Here, we…

### Effective field theory of black hole perturbations with timelike scalar profile: formulation

- PhysicsJournal of Cosmology and Astroparticle 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…

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