Signatures of Correlation of Spacetime Fluctuations in Laser Interferometers

TL;DR

This paper develops a framework linking spacetime fluctuations predicted by gravity models to laser interferometer signals, enabling better detection and understanding of these fluctuations through different interferometer designs.

Contribution

It provides a detailed correspondence between classes of spacetime fluctuations and their expected signals in various laser interferometers, aiding future experimental searches.

Findings

Laboratory interferometers can observe all characteristic signatures of SFs.

LIGO is more suited for detecting the presence or absence of SFs.

Different SF classes produce distinct, identifiable signatures in interferometer data.

Abstract

Spacetime fluctuations (SFs), a common feature of different proposed gravity models, could be detected using laser interferometers. In the search for SFs, a correspondence between the expected output signals and different gravity models is needed, both for guiding the design of future interferometers, and for identifying the signal in experimental data. In this work, we provide such a correspondence for some classes of SFs and geometries of the interferometers. We consider three different classes of SFs, characterised by the decay behaviours and symmetries of their two-point correlation functions. Our approach applies to Michelson laser interferometers with Fabry-P\'erot arm cavities such as the km-long LIGO detectors and those without arm cavities such as the laboratory-scale setups QUEST and GQuEST. Analysing the expected interferometer output signals, we identify three characteristic signatures for each class of SF. The designed broadband sensitivity of the laboratory-scale instruments would allow all characteristic signatures of the different classes of SFs to be observed, and such observations could provide more information on the nature of the SFs than those from LIGO. On the other hand, we find that LIGO is better suited for detecting the bare presence or absence of SFs.