Testing classical-quantum gravity with geodesic deviation

TL;DR

This paper investigates a semiclassical gravity model's testability using gravitational-wave data, introduces two new models, and compares their strain spectra to assess phenomenological viability.

Contribution

It analytically derives strain spectra from a novel semiclassical gravity model and proposes two additional models for comparison with observational data.

Findings

The original model's strain spectrum can be tested with current gravitational-wave sensitivity.

Two new models are constructed: a Einstein-consistent modification and an environment-induced noise model.

Comparison shows differences in strain spectra among models and perturbative quantum gravity.

Abstract

A novel semiclassical gravity model proposed by Oppenheim et al., that consistently describes interactions between quantum systems and a classical gravitational field, has recently attracted considerable attention. However, the limitations and phenomenological viability of this model have not yet been thoroughly investigated. In this work, based on the model, we study quantum fluctuations of geodesic deviation coupled with a classical gravitational field. We analytically derive the strain spectrum expected from the fluctuations and show that the original Oppenheim et al. model can be tested with the current observational sensitivity of gravitational-wave experiments. Furthermore, motivated by the novel semiclassical model, we construct two additional models: a modified Oppenheim et al. model that is manifestly consistent with Einstein equation, and a classical-quantum model with environment-induced noise. We analyze the strain spectra predicted by these two models through comparison with those of the original Oppenheim et al. model and perturbative quantum gravity.