Assessing the potential of LIGO-India in resolving the Hubble tension

Abstract

Conclusive determination of the Hubble constant ($H_0$) is a major challenge in current astronomy due to the observed discrepancies between early and late universe measurements. Joint detections of gravitational waves (GW) and electromagnetic (EM) signals from binary neutron star (BNS) mergers promise an independent probe for $H_0$. However, this requires tens of such detections, requiring decades of observation with the present detectors. LIGO-India can significantly accelerate this process. LIGO-India's addition to the detector network could boost event detections by $\sim 70\%$ and double the number of properly localized ("triple-coincidence") detections. Through end-to-end simulations, we show that LIGO-India could increase the EM follow-up rate of kilonovae by $\sim 2-7$ times, reducing the $H_0$ estimation error by a factor of $\approx 1.65-2.82$ for Vera Rubin LSST, thus significantly reducing the observation time required to attain the necessary precision. Moreover, LIGO-India can improve sky localization precision by many folds ($\sim 5$), allowing much deeper EM follow-ups, potentially reducing the time needed to resolve the "Hubble tension" from decades to a few years.