Positivity bounds on reconstructed Horndeski models

Understand

Positivity bounds provide conditions that a consistent UV-completion exists for a quantum field theory.

• We examine their application to Horndeski gravity models reconstructed from the effective field theory (EFT) of dark energy.
• This enables us to assess whether particular phenomenological parameterizations of the EFT functions reconstruct theories that respect or violate the positivity bounds.
• We find that commonly adopted EFT parametrizations, cast in terms of the dark energy density or power laws of the scale factor, only satisfy the positivity bounds in non-trivial regions of the parameter space.