Abstract
Large field inflation is arguably the simplest and most natural variant of slow-roll inflation. Axion monodromy may be the most promising framework for realising this scenario. As one of its defining features, the long-range polynomial potential possesses short-range, instantonic modulations. These can give rise to a series of local minima in the post-inflationary region of the potential. We show that for certain parameter choices the inflaton populates more than one of these vacua inside a single Hubble patch. This corresponds to a dynamical phase decomposition, analogously to what happens in the course of thermal first-order phase transitions. In the subsequent process of bubble wall collisions, the lowest-lying axionic minimum eventually takes over all space. Our main result is that this violent process sources gravitational waves, very much like in the case of a first-order phase transition. We compute the energy density and peak frequency of the signal, which can lie anywhere in the mHz-GHz range, possibly within reach of next-generation interferometers. We also note that this ``dynamical phase decomposition" phenomenon and its gravitational wave signal are more general and may apply to other inflationary or reheating scenarios with axions and modulated potentials.
Highlights
The central predictions allowing us to discriminate between inflationary models are the slow roll parameters, most prominently the tilt of the scalar power spectrum ns 0.96 and the tensorto-scalar ratio r 0.08 [1, 2]
We show that for certain parameter choices the inflaton populates more than one of these vacua inside a single Hubble patch. This corresponds to a dynamical phase decomposition, analogously to what happens in the course of thermal first-order phase transitions
In a stringy setup it is a question of moduli stabilisation: e.g. in the Large Volume Scenario (LVS) [71, 72] decay constants are generically suppressed by the volume of the compactification manifold and are naturally small
Summary
The central predictions allowing us to discriminate between inflationary models are the slow roll parameters, most prominently the tilt of the scalar power spectrum ns 0.96 and the tensorto-scalar ratio r 0.08 [1, 2]. Our message is the following: Due to the typical instantonic modulations of the potential, first order phase-transition-like, violent dynamics may occur after the end of inflation and before reheating. This leads to additional gravitational waves, which are very different in frequency from those studied in the CMB. Appendix B provides some details of an inflection point model of inflation in which our gravitational wave signal may arise
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.