Traces of a Heavy Field in Gravitational Waves

TL;DR

This paper explores how oscillations of a heavy spectator field during inflation can resonantly amplify fluctuations, leading to potentially observable gravitational waves, even without direct interactions with other fields.

Contribution

It introduces a mechanism where a heavy spectator field's oscillations induce large gravitational waves through resonance, independent of direct field interactions.

Findings

Resonant amplification of spectator field fluctuations during inflation.

Generation of large gravitational waves from heavy field oscillations.

Potential detectability of these GWs by future observations.

Abstract

We discuss gravitational waves (GWs) induced by a heavy spectator field that starts to oscillate during inflation. During the oscillation of the spectator field, its effective mass can also oscillate in some potentials. This mass oscillation can resonantly amplify the spectator field fluctuations. We show that these amplified fluctuations can induce large GWs, which could be investigated by future gravitational wave observations. This kind of induced GW can be produced even if the spectator field does not have any interaction with other fields except for gravitational interaction.