Gravitational Optics: Self-phase modulation and harmonic cascades

TL;DR

This paper explores how low amplitude gravitational waves in flat space-time exhibit nonlinear interactions similar to optical phenomena, leading to energy spreading across a broad spectrum through self-phase modulation and harmonic generation.

Contribution

It establishes an analogy between gravitational wave nonlinear interactions and optical media, highlighting third order effects like self-phase modulation and harmonic cascades in flat space-time.

Findings

Flat space-time acts as a centro-symmetric optical medium.

Third order nonlinearity causes self-phase modulation.

Energy of gravitational waves disperses over a broad spectral range.

Abstract

Nonlinear wave interaction of low amplitude gravitational waves in flat space-time is considered. Analogy with optics is established. It is shown that the flat metric space-time is equivalent to a centro-symmetric optical medium, with no second order susceptibility. The lowest order nonlinear effects are those due to the third order nonlinearity and include self-phase modulation and high harmonic generation. These processes lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range.