Parameterized Frameworks for Testing Gravity with Black Hole Electromagnetic Observations

• Applicant: Dr. Dimitry Ayzenberg, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 510156288

Black holes are the most extreme gravitational objects in the universe, i.e. they have the strongest gravitational fields and the largest spacetime curvatures, making black holes and their vicinity perfect for studying and testing gravity. Electromagnetic emission from the accretion disks around black holes is strongly influenced by the properties of both the disk and the black hole spacetime, allowing for probes of the extreme spacetime near black holes and for tests to determine if Einstein's Theory of General Relativity is the correct description for gravity. However, to do so requires tools that can properly distinguish between modified gravity theories and different accretion disk models, and these are currently lacking. The goal of this project is to develop a parameterized framework that will allow for tests of gravity with black hole electromagnetic observations without the need for computationally and time costly analyses. The current analysis methodology requires one to simulate observations in specific modified gravity theories, which is quite inefficient given the large amount of modified theories and solutions. By developing a parameterized framework that encodes the most important modifications to the black hole solution and General Relativity, the analysis can be reduced to simply fitting the observational data to estimate parameters and then, through the framework, mapping those to any theory one wishes to study. Similar frameworks known as the parameterized post-Newtonian and parameterized post-Einsteinian frameworks have been very instrumental in tests of gravity in solar system based observations and detections of gravitational waves. An additional framework will be developed to encode modifications to the standard thin-disk model used for black hole accretion disks, extending work that has already been completed by myself and collaborators as well as others. Using both frameworks, a combined framework allowing for simultaneous tests of gravity and accretion disk models will also be created. All frameworks will be applied to available observational data and, depending on the quality of data, constraints will be placed on both modifications to General Relativity and the thin-disk model.

• DFG Programme: Research Grants
• International Connection: China, Netherlands
• Cooperation Partners: Professor Dr. Cosimo Bambi; Dr. Victoria Grinberg