https://doi.org/10.1140/epjc/s10052-020-7973-z
Regular Article – Theoretical Physics
Positivity in the effective field theory of cosmological perturbations
1
School of Physics, University of Chinese Academy of Sciences, Beijing, 100049, China
2
Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing, 100190, China
* e-mail: yegen14@mails.ucas.ac.cn
Received:
28
November
2019
Accepted:
26
April
2020
Published online:
14
May
2020
Requiring the existence of a unitary, causal and local UV-completion places a set of positivity bounds on the corresponding effective field theories (EFTs). We discuss the obstructions and possibility in applying the positivity bound to cosmology, in particular the EFT of cosmological perturbations. Taking a 
beyond-Horndeski EFT as an illustrative example, we derive such bounds, which incorporate the cosmological correction of order 
, 
being the cutoff scale. The derived bounds are applied to slow-roll inflation with beyond Horndeski operators. It is found that the cosmological positivity bounds may be either stronger or weaker than their flat space counterpart.
© The Author(s), 2020
