Inflationary Phase Transitions in the Early Universe: A Bayesian Study with Space-Based Gravitational Waves Detectors

TL;DR

This paper assesses how future space-based gravitational wave detectors can identify and analyze signals from inflationary phase transitions, providing a realistic framework for probing early universe physics.

Contribution

It develops a comprehensive data-analysis framework incorporating noise and foregrounds, and evaluates detection and parameter reconstruction capabilities for inflationary signals.

Findings

Detection feasible at moderate SNRs

Stronger signals enable better parameter estimation

Realistic assessment of future detector capabilities

Abstract

Phase transitions during inflation can generate a stochastic gravitational-wave background that probes primordial physics. We study the detectability and parameter reconstruction of such a signal with a space-based gravitational-wave detector. Using a Taiji-like mission as a benchmark, we construct a realistic data-analysis framework that includes instrumental noise, astrophysical foregrounds and backgrounds, and the $A$, $E$, and $T$ time-delay interferometry channels. The target signal is described in a minimal, model-independent form and analyzed using both Fisher-matrix forecasts and Bayesian inference with nested sampling. We quantify detection significance and parameter-recovery thresholds, showing that while detection is achievable at moderate signal-to-noise ratios, stronger signals provide more reliable parameter reconstruction. These results offer a realistic assessment of the capability of future space-based missions to probe phase transitions during inflation through stochastic gravitational radiation.