Proposal for a geophysical search for dilatonic waves

TL;DR

This paper proposes a novel method using superconducting gravimeters to detect dilatonic waves predicted by string theories, focusing on Earth's surface-gravity changes at very low frequencies, and presents preliminary upper limits on dilaton energy density.

Contribution

It introduces a new low-frequency search method for dilatonic waves based on Earth's surface gravity variations, expanding detection possibilities beyond existing gravitational-wave detectors.

Findings

Preliminary upper limits on dilaton energy density at low frequencies.

Method shows potential to detect dilatonic waves in a new frequency window.

Current results limited by Earth's model uncertainties.

Abstract

We propose a new method of searching for the composition-dependent dilatonic waves, predicted by unified theories of strings. In this method, Earth's surface-gravity changes due to translational motions of its inner core, excited by dilatonic waves, are searched for by using superconducting gravimeters. This method has its best sensitivity at the frequency of $\sim$ 7 $\times$ 10$^{-5}$ Hz, which is lower than the sensitive frequencies of previous proposals using gravitational-wave detectors: $\sim$ 10 to 1000 Hz. Using available results of surface-gravity measurements with superconducting gravimeters and assuming a simple Earth model, we present preliminary upper limits on the energy density of a stochastic background of massless dilatons at the low frequency. Though the results are currently limited by the uncertainty in the Earth model, this method has a potential of detecting dilatonic waves in a new window.