The Cosmological Potential of Gravitational Wave Memory with Future Detectors

by Dr Susmita Jana (APCTP)

Thursday 8 May 2025, 16:00 → 18:00 Asia/Seoul

B447-1

While the ΛCDM model successfully explains the late-time accelerated expansion of the universe, accumulating observational evidence suggests significant deviations from this standard cosmological framework. Determining the correct cosmological model and its parameters remains a crucial open problem in gravity and cosmology. Leveraging the enhanced sensitivity of next-generation gravitational wave (GW) detectors at high redshifts, up to z ~ 100, we propose that GW memory in a cosmological background provides a novel avenue for constraining cosmological model parameters. GWs, originating from astrophysical events, perturb the 2-D surface orthogonal to their propagation direction, generating secondary GWs and inducing a permanent distortion, or ‘memory,’ in this surface. As this memory propagates over cosmological distances, it accumulates the integrated effect of the background, encoding the cosmological signature. We demonstrate a significant amplification of this integrated cosmological memory (ICM) with distance, specifically showing an enhancement of up to a factor of 100 for sources at z ~ 10 — well within the sensitivity range of next-generation detectors like Cosmic Explorer and the Einstein Telescope. Furthermore, we investigate the implications of parity-violating dynamical Chern-Simons (dCS) gravity, showing that if the astrophysical event produces GWs with different amplitudes in the plus and cross polarization modes, this initial amplitude difference is also amplified through the ICM. Finally, we demonstrate that the distinct amplification of the ICM for the two polarization modes provides an independent constraint on the dCS parameter (α), achievable with next-generation GW detectors.