Speaker
Description
The stochastic gravitational-wave backgrounds are expected to arise from the superposition of many individually unresolved sources throughout cosmic history, carrying information about compact-binary populations, gravity beyond general relativity, and possible processes in the early Universe. In this talk, I will present recent progress in the LIGO-Virgo-KAGRA search for an isotropic gravitational-wave backgrounds using cross-correlation measurements between ground-based detectors. I will first describe updates to the analysis, with particular emphasis on new frequency-domain cuts designed to identify and remove narrowband instrumental artifacts while preserving sensitivity to broadband stochastic signals.
I will then discuss the search for a power-law gravitational-wave background with spectral index 2/3, as predicted for a background dominated by inspiralling compact binaries, and compare the observational constraints with predicted compact-binary coalescence backgrounds based on GWTC population models. Beyond the standard tensor-polarized background, I will also summarize searches for non-GR polarization components, including possible scalar and vector modes, and their implications for alternative theories of gravity. Since correlated magnetic noise can mimic a stochastic signal, I will further review the magnetic-noise budget and its impact on the interpretation of the search.
Finally, following the collaboration results, I will introduce recent work on inflation-era phase transitions as a potential cosmological source of stochastic gravitational waves. This provides a complementary perspective on how current gravitational-wave background searches can constrain early-Universe physics and highlights the discovery potential of future ground-based detectors.