Probing the quantum gravitational structure of spacetime via black holes and gravitational waves

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The two fundamental pillars of modern physics are General Relativity (GR) and Quantum Field Theory (QFT). GR describes classical spacetime and phenomena in which gravity is very strong. QFT describes quantum phenomena and physics at small scales. Phenomena in which both gravitational and quantum effects are significant cannot be studied using either of these theories alone and require a certain consistent combination of GR and QFT. This combination is a theory under development called Quantum Gravity (QG). Full development of this theory has proven to be very challenging. Once completed, QG is expected to provide us with a detailed knowledge of the most fundamental aspects of the Universe, particularly, the quantum structure of spacetime. Knowledge gained about this structure will answer many important questions, including the dynamics of the interior of quantum black holes, the nature of their singularities, and the behavior of nature at the quantum epoch of cosmology. Finding a full theory of QG is considered to be the final goal of modern physics. The long-term goal of my research program is to make significant contributions toward finding a full theory of QG. I will use several short-term goals to achieve this objective. Part of these goals center around studying various obstacles in combining GR and QFT and providing resolutions for them. As previously noted, the obstacles are deeply related to the fundamental nature of spacetime. An important question I will try to answer is "how does spacetime look in very small (quantum) scales?" Another longstanding issue is "how does quantum spacetime become the classical spacetime at larger scales?" To provide answers to these questions, I will search for important hints about the nature of spacetime from both theory and phenomenology. I will use two main natural laboratories: black holes and Gravitational Waves (GWs)/Gamma Ray Bursts (GRBs). Black holes are one of the most important playgrounds of QG. I will study quantum black holes and their interactions with matter fields to find important deviations from classical physics rooted in QG. This study will also serve as a standalone investigation into quantum black holes. GWs and GRBs travel from their source over cosmological distances before being detected by instruments such as the Laser Interferometer Gravitational-wave Observatory (LIGO.) If spacetime has a quantum fine structure, it will imprint certain signatures on these waves that can be observed by experiments. I will investigate and derive these signatures and compare them with LIGO observations to obtain valuable information about both the nature of QG and spacetime. This also serves towards bridging the gap that currently exists between QG theory and experiment. My proposed research will make a significant contribution to the full development of QG which is of major importance to modern physics. It will also raise the profile of Canadian scientific contribution in this area.