GRMHD and GRRT Simulations of Black Hole Accretion: Flares, Precession, and Complex Spacetimes

This dissertation studies the electromagnetic signatures of accreting supermassive black holes using general relativistic magnetohydrodynamic simulations and covariant radiative-transfer calculations. The new analysis still awaits peer review, but it already lays out the central claim clearly.

It is relevant because astrophysics becomes persuasive only when an observed signal can be tied to a physically defensible explanation. Compact objects such as neutron stars and black holes are natural laboratories for extreme physics, but the distance and complexity of these systems make interpretation difficult without multi-wavelength coverage and careful modeling. A detection without a mechanism is only half a result. the other half comes from showing that the signal fits quantitatively inside a coherent physical picture rather than merely being consistent with a broad family of models. It develops a unified numerical framework for modeling black-hole accretion, jet launching, flaring activity, and multi-band variability in Kerr, non-Kerr, and binary black-hole. For isolated Kerr black holes, I investigate how magnetic-field geometry affects accretion dynamics and transient emission.

Multi-loop magnetic configurations naturally produce reconnection events and flux-rope structures that can power near-infrared flares from Sagittarius A*, while the evolving. I also show that in tilted magnetically arrested disks, magnetic torques can drive retrograde disk and jet precession.

The dissertation then applies the same framework to more complex spacetimes. Simulations of accretion onto regular loop-quantum black holes show that quantum-gravity corrections can modify photon-ring size, polarization structure, and jet power, leading to.

Finally, simulations of supermassive binary black holes in time-dependent spacetimes reveal how gravitational self-lensing, shock activity, and spin-orbit coupling shape. Together, these results connect relativistic plasma dynamics with current and future observations of black-hole systems.

The broader interest lies in turning an observational clue into something that can be weighed against competing models of the underlying physics. Astrophysics does not have the luxury of controlled experiments; everything is inferred from radiation that traveled across cosmic distances under conditions that cannot be reproduced in a terrestrial laboratory. This makes the interpretation chain longer and more uncertain than in bench science, but it also means that a well-constrained measurement of an extreme object carries theoretical information that no earthbound experiment can provide.

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Because this is still a preprint, the result should be read with genuine interest and proportionate caution. Peer review is not a guarantee of correctness, but it is a process that forces authors to respond to technical criticism from specialists who have no stake in a particular outcome. Preprints that survive that process, often with substantive revisions, emerge with a stronger evidential base than the version that first appeared. Until that stage is complete, the responsible reading keeps uncertainty explicitly visible rather than treating the claims as established findings.

The next step is to see whether independent datasets and physical modeling converge on the same interpretation. Multi-wavelength follow-up, combining X-ray, radio and optical data where possible, is typically what separates a compelling detection from a robust physical characterization. In high-energy astrophysics, results that initially looked definitive have been revised when data from a second messenger arrived; the current result should be read with that history in mind. Until peer review and independent follow-up address those open questions, skepticism is not a failure of appreciation for the work; it is part of how science decides what to keep.

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