Stochastic backgrounds of gravitational waves and spherical detectors

TL;DR

This paper analyzes how a stochastic gravitational wave background interacts with spherical detectors, providing explicit response functions and discussing the challenges and improvements in signal detection depending on prior knowledge of the GW spectrum.

Contribution

It offers detailed expressions for spherical detector responses to stochastic gravitational waves and assesses detection capabilities with and without prior spectral knowledge.

Findings

Single spherical detectors struggle to distinguish signals without prior spectral knowledge.

Prior knowledge of GW spectral density enhances detection due to spherical detector's multimode features.

Explicit response functions facilitate better understanding of detector sensitivity to stochastic backgrounds.

Abstract

The analysis of how a stochastic background of gravitational radiation interacts with a spherical detector is given in detail, which leads to explicit expressions for the system response functions, as well as for the cross-correlation matrix of different readout channels. It is shown that distinctive features of GW induced random detector excitations, relative to locally generated noise, are in practice insufficient to separate the signal from the noise by means of a single sphere, if prior knowledge on the GW spectral density is nil. The situation significantly improves when such previous knowledge is available, due to the omnidirectionality and multimode capacities of a spherical GW antenna.