English

Avoiding the string swampland in single-field inflation: Excited initial states

High Energy Physics - Theory 2019-03-06 v2 Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology

Abstract

One class of single-field inflationary models compatible with the recently-conjectured Swampland criteria would be those in which a Hubble slow-roll parameter ϵH\epsilon_\text{H} is not the same as ϵV(V/V)2\epsilon_\text{V} \sim (V'/V)^2. However, a roadblock for these models (with a convex potential) lie in the unacceptably high tensor-to-scalar ratio, rr, generically predicted by them. In this work, illustrating through an explicit example, we point out that having a non-Bunch-Davies component to the initial state of cosmological perturbations makes the value of rr compatible with observations. In this way, we lay down a new path even for standard models of slow-roll inflation to be consistent with the Swampland criteria by invoking deviations from the Bunch-Davies initial state.

Keywords

Cite

@article{arxiv.1809.01277,
  title  = {Avoiding the string swampland in single-field inflation: Excited initial states},
  author = {Suddhasattwa Brahma and Md. Wali Hossain},
  journal= {arXiv preprint arXiv:1809.01277},
  year   = {2019}
}

Comments

9 pages; comments welcome; v2: version accepted in JHEP

R2 v1 2026-06-23T03:54:29.494Z