Research Projects

Einstein's General Theory of Relativity (GR) faces profound challenges in explaining dark energy, dark matter, and quantum gravity. The emergence of multimessenger astronomy --- combining gravitational waves (GWs), electromagnetic signals, and cosmological surveys --- now enables unprecedented tests of GR across all curvature regimes, from the strong-field dynamics of merging compact objects to the large-scale evolution of the Universe. However, current approaches remain fragmented, leaving a critical curvature gap in our understanding of gravity. This project will develop a unified framework to bridge this gap, specifically optimized for India's upcoming LIGO-India observatory, while synergizing with other electromagnetic facilities like SKA. At the core of our methodology lies three advancements. First, we will develop and apply the novel Integrated Cosmological Memory (ICM) effect to measure cosmic expansion history directly from GW data, bypassing systematics inherent in traditional electromagnetic probes. Second, we will establish electromagnetic counterparts of GW events as precision laboratories for studying strong-field gravity, extracting information about central engine physics that is inaccessible through GWs alone. Finally, we will conduct the unified, multi-scale tests of gravity. These interconnected approaches will create the most comprehensive testbed for GR to date. The outcomes of this research will deliver the first complete framework for testing gravity across different curvature scales, from event horizons of primordial black holes (PBHs) to cosmological distances. Our analysis will maximize the scientific return from this facility, particularly in the mid-band GW spectrum, where it offers unique sensitivity. The project will place new constraints on beyond-GR theories with up to an order-of-magnitude improvement over current limits. By unifying gravity tests across the curvature spectrum and developing novel probes of fundamental physics, this work will position India at the forefront of theoretical and observational gravity research in the multimessenger era while paving the way for resolving some of the most pressing mysteries in modern cosmology.