ExGrav

Extreme gravity with electromagnetic and gravitational waves

01/12/2021 to 31/05/2023

Theories of gravity describe the effect of gravitation on spacetime and matter in our universe. The leading theory of gravity today is Einstein’s theory of general relativity. While largely successful, some shortcomings of general relativity, originating from theoretical considerations like singularities and ob-servational considerations like dark matter/dark energy, have led to modifications and extensions of the theory. This project aims to study the nature of gravity in our universe by analyzing its behavior in black hole neighborhoods. Black holes are the ideal candidates for such tests since they are gravi-tationally compact, parametrically simple (at least in general relativity) and astrophysically numerous. We plan to build mathematical and computational models to quantify the effects of deviations, both theory-specific and theory-independent, from Einstein’s theory on gravitational and electromagnetic observables. We plan to use these models to analyze data from ground-based gravitational wave de-tectors (LIGO and VIRGO) and put astrophysical constraints on such deviations. We also plan to use simulated data from upcoming space-based gravitational wave detectors (LISA, TianQin, etc.) and X- ray detectors (XRISM, Athena, etc.) to estimate the several-orders-of-magnitude improvements they will provide over existing constraints, acting as highly precise space laboratories for testing Einstein’s theory. We will also explore the possibilities of doing pathbreaking science with new phenomena and tests that will become accessible after these instruments are live.
I have significant research experience with electromagnetic waves (in particular, X-ray) based tests of theories of gravity, and I am beginning to explore gravitational waves based tests. The Theoretical Astrophysics group of the Institut für Astronomie und Astrophysik (IAAT) at the University of Tübingen, Germany, led by Prof. Kostas Kokkotas is among the best, in Germany and the world, for studying modified theories of gravity and black holes in those theories, and I would like to choose them as my German host. The Institute of Fundamental Physics (IFPU) in Trieste, Italy, is a joint initiative of the International School for Advanced Studies (SISSA), the Abdus Salam International Centre for Theoretical Physics (ICTP), the National Institute for Astrophysics (INAF) and the National Institute for Nuclear Physics (INFN), focussed on exploring the fundamental laws of nature. In particular, Prof. Barausse of IFPU is a world leader in gravitational wave physics and alternative theories of gravity. He is the Principal Investigator of the European Research Council’s Consolidator Grant GRAMS and his group is working on using gravitational waves to unravel the fundamental nature of gravity. I would like to choose him as my foreign host. With the expertise of IFPU and IAAT in gravitational waves and modified theories of gravity, and my background and experience with performing tests of gravity, we expect a highly successful collaboration, resulting in answers to some fundamental questions about gravity and unravelling of brand new research avenues.