Scale-invariant spectrum of Lee-Wick model in de Sitter spacetime

Understand

We obtain a scale-invariant spectrum from the Lee-Wick model in de Sitter spacetime.

• This model is a fourth-order scalar theory whose mass parameter is determined by $M^2=2H^2$.
• The Harrison-Zel'dovich scale-invariant spectrum is obtained by Fourier transforming the propagator in position space as well as by computing the power spectrum directly.
• It shows clearly that the LW scalar theory provides a truly scale-invariant spectrum in whole de Sitter, while the massless scalar propagation in de Sitter shows a scale-invariant spectrum in the superhorizon region only.