Non-local parameter degeneracy in the intrinsic space of gravitational-wave signals from extreme-mass-ratio inspirals

TL;DR

This paper investigates the non-local correlations and degeneracies in the space of gravitational-wave signals from extreme-mass-ratio inspirals, highlighting their impact on LISA data analysis and proposing new analysis tools.

Contribution

It introduces new analysis tools and provides a comprehensive qualitative study of signal degeneracy and its implications for gravitational-wave data analysis.

Findings

Degeneracy is widespread in the continuum of signals.

Non-local correlations hinder signal detection in LISA data.

Realistic signals are less affected by degeneracy than theoretical models.

Abstract

Extreme-mass-ratio inspirals will be prized sources for the upcoming space-based gravitational-wave observatory LISA. The hunt for these is beset by many open theoretical and computational problems in both source modeling and data analysis. We draw attention here to one of the most poorly understood: the phenomenon of non-local correlations in the space of extreme-mass-ratio-inspiral signals. Such correlations are ubiquitous in the continuum of possible signals (degeneracy), and severely hinder the search for actual signals in LISA data. However, they are unlikely to manifest in a realistic set of putative signals (confusion). We develop an inventory of new analysis tools in order to conduct an extensive qualitative study of degeneracy - its nature, causes, and implications. Previously proposed search strategies for extreme-mass-ratio inspirals are reviewed in the light of our results, and additional guidelines are suggested for the scientific analysis of such sources.