Detection of extremely low frequency gravitational wave using gravitational lens

TL;DR

This paper proposes that gravitational lensing, specifically Einstein rings, can be used to detect extremely low frequency cosmological gravitational waves by observing induced time delays across the ring.

Contribution

It introduces a novel method of gravitational wave detection using gravitational lensing effects, focusing on Einstein rings in aligned configurations.

Findings

Aligned lens systems can reveal gravitational wave effects through time delays.

Gravitational lensing can mimic nonaligned configurations in the presence of gravitational waves.

Potential for detecting extremely low frequency gravitational waves with current observational setups.

Abstract

The effect of gravitational wave of cosmological wavelength on the gravitational lensing is investigated. When the source, deflector, and observer are aligned in a highly symmetric configuration, an Einstein ring will be observed by the observer. There will be no time delays between different locations on the Einstein ring in the absence of gravitational wave. Otherwise, time delays between different locations on the Einstein ring will emerge if cosmological gravitational wave propagates through the system. Previous studies demonstrated that the time delay resulting from the aligned source-deflector-observer configuration in the presence of gravitational wave of cosmological wavelength could be equivalent to that of a similar lens with a nonaligned source-deflector-observer configuration in the absence of gravitational wave. Results in this work show that gravitational lens with the aligned source-deflector-observer configuration could serve as a potential gravitational wave detector when the whole Einstein ring observed by the observer is taken into account.