Power spectrum oscillations from Planck-suppressed operators in effective field theory motivated monodromy inflation

Abstract

We consider a phenomenological model of inflation where the inflaton is the phase of a complex scalar field $\Phi$. Planck-suppressed operators of $\mathcal{O}(f^5/M_{\mathrm{pl}})$ modify the geometry of the vev $⟨\Phi ⟩$ at first order in the decay constant $f$, which adds a first order periodic term to the definition of the canonically normalized inflaton $\varphi$. This correction to the inflaton induces a fixed number of extra oscillatory terms in the potential $V\sim {\theta }^p$. We derive the same result in a toy scenario where the vacuum $⟨\Phi ⟩$ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale $k$ and provide a possible mechanism for differentiating EFT-motivated inflation from models where the angular shift symmetry is a gauge symmetry.

Comments: 12 pages, 6 figures; matches published version