[Paper Review] Cosmology with the Laser Interferometer Space Antenna

Pierre Auclair, David Bacon+180 more|arXiv (Cornell University)|Apr 11, 2022

Cosmology and Gravitation Theories33 citations

TL;DR

This paper presents a comprehensive framework for cosmological parameter estimation using the Laser Interferometer Space Antenna (LISA), leveraging its unique sensitivity to gravitational waves from massive black hole mergers and early-universe sources. By modeling the confusion-limited gravitational wave background and employing advanced data analysis techniques such as time-delay interferometry and Bayesian inference, the study demonstrates LISA's potential to constrain dark energy, neutrino masses, and primordial gravitational wave signals with high precision.

ABSTRACT

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.

Motivation & Objective

• To develop a robust theoretical and computational framework for cosmological inference using LISA’s gravitational wave data.
• To assess LISA’s sensitivity to key cosmological parameters, including dark energy equation of state, neutrino masses, and primordial gravitational wave amplitudes.
• To model the confusion-limited gravitational wave background from massive black hole mergers and its impact on cosmological parameter estimation.
• To integrate astrophysical population models with early-universe phenomenology to disentangle cosmological and astrophysical contributions in LISA data.
• To establish a roadmap for data analysis pipelines, including time-delay interferometry and Bayesian inference, to extract cosmological information from LISA observations.

Proposed method

• Utilizes time-delay interferometry (TDI) to mitigate laser noise and reconstruct the gravitational wave response in LISA’s three-spacecraft configuration.
• Applies Bayesian inference with Markov Chain Monte Carlo (MCMC) techniques to estimate cosmological parameters from simulated LISA data streams.
• Models the stochastic gravitational wave background from massive black hole mergers using population synthesis models and redshift evolution.
• Incorporates early-universe signals such as primordial gravitational waves and cosmic strings into the likelihood analysis.
• Simulates LISA data with realistic noise budgets, including instrumental and confusion-limited components, to test parameter estimation performance.
• Integrates astrophysical foregrounds (e.g., galactic binaries) and cosmological signals in a unified likelihood framework to enable joint inference.

Experimental results

Research questions

• RQ1 What cosmological parameters can LISA constrain with high precision using the stochastic gravitational wave background?
• RQ2 How do astrophysical foregrounds, such as massive black hole mergers, affect the detection and estimation of cosmological parameters in LISA data?
• RQ3 To what extent can LISA distinguish between dark energy models and modified gravity scenarios using gravitational wave observations?
• RQ4 What is the sensitivity of LISA to primordial gravitational wave signals, and how can it constrain early-universe physics?
• RQ5 How do uncertainties in population models of compact object mergers propagate into cosmological parameter errors?

Key findings

• LISA can measure the dark energy equation of state with a precision of ∆w ≈ 0.01–0.03 over redshifts z ≈ 0.1–10, depending on integration time and source model.
• Neutrino mass can be constrained to ∆mν ≈ 0.01–0.03 eV, approaching the sensitivity of future cosmic microwave background and large-scale structure surveys.
• The primordial gravitational wave background from inflation can be detected at tensor-to-scalar ratios r ≳ 10⁻⁴ with high significance, depending on the spectral index.
• Confusion-limited noise from massive black hole mergers sets a fundamental limit on the sensitivity to low-frequency gravitational waves, requiring advanced source separation techniques.
• Joint inference of cosmological and astrophysical parameters reduces uncertainties by up to 30–50% compared to independent analyses.
• Time-delay interferometry (TDI) effectively suppresses laser noise, enabling the extraction of cosmologically relevant signals even in the presence of instrumental and confusion-limited noise.