https://doi.org/10.1140/epjp/i2019-12529-x
Regular Article
UV physics and the speed of sound during inflation
Departamento de Física Teórica and Instituto de Fısica Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain
* e-mail: fgpedro@gmail.com
Received:
6
April
2018
Accepted:
21
January
2019
Published online:
9
May
2019
We consider inflation as an effective field theory and study the effects of the addition to the Lagrangian of irrelevant operators with higher powers of first derivatives on its dynamics and observables. We find that significant deviations from the two-derivative dynamics are possible within the regime of validity of the effective field theory. Focusing on monomial potentials we show that the main effect of the terms under consideration is to reduce the speed of sound thereby reducing the tensor fraction, while having little impact on the scalar tilt. Crucially, these effects can arise even when the UV cut-off is well above the inflationary Hubble parameter.
© Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature, 2019
