Horizon crossing and inflation with large η

By W. Kinney. 2005

347 citations recorded by the source corpus.

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 be valid. This relation is satisfied for the usual cases of power-law and slow-roll inflation. I then consider a model for which the relation is strongly violated, and the curvature perturbation evolves rapidly on superhorizon scales. This model has Hubble slow-roll parameter {eta}=3, but predicts a scale-invariant spectrum of density perturbations. I consider the case of hybrid inflation with large {eta}, and show that such solutions do not solve the '{eta} problem' in supergravity. These solutions correspond to field evolution which has not yet relaxed to the inflationary attractor solution, and may make possible new, more natural models on the string landscape.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Oceanography

View Paper: https://www.semanticscholar.org/paper/6e4b63fa18f3531f018a48f9b48d5415d9291b64

How researchers see this paper

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In Astronomy and Astrophysics

1. C. Byrnes
2. Yi-Fu Cai
3. S. Patil
4. A. Kehagias
5. Tsutomu Kobayashi
6. Xingang Chen
7. Misao Sasaki
8. M. H. Namjoo

In Nuclear and High Energy Physics

1. C. Byrnes
2. A. Kehagias
3. Yi-Fu Cai
4. Tsutomu Kobayashi
5. S. Patil
6. Xingang Chen
7. P. S. Cole
8. G. Tringas

In Oceanography

1. C. Byrnes
2. Misao Sasaki
3. M. H. Namjoo
4. P. S. Cole
5. Xingang Chen
6. Tsutomu Kobayashi
7. A. Kehagias
8. S. Patil

Citations in the corpus

• Primordial black holes from α-attractors (2018, background): “In between the initial and the final slow-roll phase there is a stage known as ultra slow-roll (USR) phase [36].”
• Horndeski theory and beyond: a review (2019, background): “Note, however, that even in the case of general relativity + a canonical scalar field the ultra slow-roll/nonattractor phase of inflation can appear, in which we have GS ∝ a and the second term grows [72, 73].”
• Steepest growth of the power spectrum and primordial black holes (2018, background): “As verified explicitly through a potential reconstruction exercise in appendix C, we indeed see that a phase of Ultra Slow-Roll (USR) inflation [44, 45], defined as a phase of constant η = −6, is attained as one approaches an inflection point, which can also be reasonably well approximated by a smal”
• Revisiting non-Gaussianity from non-attractor inflation models (2017, background): “for sufficiently large regime one has V (φ) ' V0 [16, 17].”