Detecting Free-Mass Common-Mode Motion Induced by Incident Gravitational Waves: Testing General Relativity and Source Direction via Fox-Smith and Michelson Interferometers

TL;DR

This paper proposes a modified interferometer setup that can detect both differential and common-mode responses to gravitational waves, aiding in source localization and testing gravity theories, with methods to mitigate laser noise.

Contribution

It introduces a Fox-Smith based interferometer configuration sensitive to common-mode motion, enhancing gravitational wave detection capabilities beyond traditional Michelson designs.

Findings

Able to discriminate source direction using common-mode response

Proposed noise cancellation method for laser frequency fluctuations

Potential for parallel operation with existing detectors

Abstract

In this paper we show that information on both the differential and common mode free-mass response to a gravitational wave can provide important information on discriminating the direction of the gravitational wave source and between different theories of gravitation. The conventional Michelson interferometer scheme only measures the differential free-mass response. By changing the orientation of the beam splitter, it is possible to configure the detector so it is sensitive to the common-mode of the free-mass motion. The proposed interferometer is an adaptation of the Fox-Smith interferometer. A major limitation to the new scheme is its enhanced sensitivity to laser frequency fluctuations over the conventional, and we propose a method of canceling these fluctuations. The configuration could be used in parallel to the conventional differential detection scheme with a significant sensitivity and bandwidth.