Climbing over the potential barrier during inflation via null energy condition violation

TL;DR

This paper proposes a single-field inflation model where NEC violation allows the scalar field to overcome high potential barriers, resulting in distinctive features in the primordial gravitational wave spectrum.

Contribution

It introduces a novel inflationary scenario with NEC violation enabling barrier crossing, affecting gravitational wave signatures in a unique way.

Findings

Primordial gravitational wave spectrum shows a blue tilt at middle frequencies.

The spectrum exhibits diminishing oscillations at higher frequencies.

On large and small scales, the power spectrum remains nearly scale-invariant.

Abstract

The violation of the null energy condition (NEC) may play a crucial role in enabling a scalar field to climb over high potential barriers, potentially significant in the very early universe. We propose a single-field model where the universe sequentially undergoes a first stage of slow-roll inflation, NEC violation, and a second stage of slow-roll inflation. Through the NEC violation, the scalar field climbs over high potential barriers, leaving unique characteristics on the primordial gravitational wave power spectrum, including a blue-tilted nature in the middle-frequency range and diminishing oscillation amplitudes at higher frequencies. Additionally, the power spectrum exhibits nearly scale-invariant behavior on both large and small scales.