Simple bounds from the perturbative regime of inflation

2008/02/29 by Louis Leblond, Sarah Shandera · 1 citation
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph #hep-ph #hep-th

paper · pdf · doi:10.1088/1475-7516/2008/08/007

published as JCAP0808:007,2008 · 26 pages, 4 figures, v3; added references and clarifications, typos corrected, published version

arxiv created 2008/07/11 · openalex publication_date 2008/08/06 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30

Abstract

We examine the conditions under which a perturbative expansion around an inflating background is valid. When inflation is driven by a single field with a general sound speed, we find a lower limit on the sound speed related to the amplitude of the inflationary power spectrum. Generalizing the sound speed constraints to include scale dependence can limit the number of e-folds obtained in the perturbative regime and restrict otherwise apparently viable models. We also show that, for models with a low sound speed, eternal inflation cannot occur in the perturbative regime.

Citations

• Non-Gaussianity and cosmic uncertainty in curvaton-type models
• Is brane inflation eternal?
• Non-Gaussian features of primordial fluctuations in single field inflationary models
• Large volume axionic Swiss cheese inflation
• String cosmology: a review
• Causality, Analyticity and an IR Obstruction to UV Completion
• Axion inflation in type II string theory
• N-flation
• Assisted inflation

Cited by

• Eternal inflation and a thermodynamic treatment of Einstein's equations