Probing Two-Field Open Inflation by Resonant Signals in Correlation Functions

TL;DR

This paper derives oscillatory signals in correlation functions caused by resonances in two-field open inflation, which could serve as probes of the curvature dominated phase and support the string landscape hypothesis if detected.

Contribution

It introduces a method to identify oscillatory signatures in correlation functions from two-field open inflation, linking them to the curvature dominated phase and providing bounds on oscillation amplitudes.

Findings

Distinct oscillations in power and bi-spectrum identified

Detection prospects discussed, with challenges acknowledged

Upper limits on heavy field oscillation amplitudes derived

Abstract

We derive oscillatory signals in correlation functions in two-field open inflation by means of the in-in formalism; such signatures are caused by resonances between oscillations in the tunnelling field and fluctuations in the inflaton during the curvature dominated, intermediate and subsequent inflationary regime. While amplitudes are model-dependent, we find distinct oscillations in the power and bi-spectrum that can act as a direct probe of the curvature dominated phase and thus, indirectly, strengthen the claim of the string landscape if they were observed. We comment on the prospects of detecting these tell-tale signs in current experiments, which is challenging, but not impossible. At the technical level, we pay special attention to the applicability conditions for truncation fluctuations to the light (inflaton) field and derive upper limits on the oscillation amplitude of the heavy field. A violation of these bounds requires a multi-field analysis at the perturbed level.