Research Projects

We are living in a remarkable era where technological advances allow us to probe the nature of gravity and exotic astrophysical objects such as black holes with unprecedented precision. Recent breakthroughs in very-long-baseline interferometry (VLBI), particularly the imaging of black holes by the Event Horizon Telescope (EHT), have opened a powerful observational window into the strong-field regime of general relativity (GR). The silhouette or “shadow” cast by a black hole, formed by photons orbiting near the photon sphere before escaping to a distant observer serves as a direct probe of spacetime geometry in the near-horizon region. This is where general relativity (GR) may be pushed to its limits and effects of new gravitational physics may begin to emerge. Motivated by these developments, the proposed research aims to construct a robust theoretical framework for analyzing black hole shadows as diagnostic tools, enabling us to distinguish between classical, quantum, and environmental influences. The central idea is that detailed features of the shadow, its shape, size, asymmetry, intensity profile, and substructure encode rich information about the underlying spacetime geometry, allowing for stringent tests of GR and its possible extensions. Specifically, the project will examine how deviations from the standard Kerr geometry, arising from quantum corrections, modified gravity theories, or the presence of exotic compact objects (ECOs), affect shadow observables. This includes horizonless configurations such as boson stars, gravastars, and traversable wormholes, which lack an event horizon and are expected to exhibit distinctive lensing patterns and brightness features. In parallel, the study will incorporate the impact of realistic astrophysical environments, such as accretion flows, magnetized plasmas, and dark matter halos, which can significantly alter photon propagation and modify the observed shadow. A key focus will be the analysis of non-integrable black hole spacetimes i.e. geometries for which the geodesic equations are not fully separable and the photon dynamics exhibit chaotic behavior. Unlike Kerr black holes, where symmetry and integrability allow clean identification of photon regions and shadow edges, non-integrable spacetimes (e.g., bumpy black holes or generic deviations from axisymmetry) lead to complex shadow boundaries, possible fractal photon ring structures, and non-trivial time-delay signatures. These features, while are challenging to compute, offer unique opportunities for testing gravitational dynamics in a less idealized setting. The project will explore such systems using perturbative and numerical tools, extending shadow analyses beyond the confines of analytically tractable geometries. To this end, the methodology will combine analytical techniques such as expansions of geodesic motion and effective potentials with advanced ray-tracing simulations to reconstruct black hole shadows as seen by distant observers. Important observables including photon regions, Lyapunov exponents, deflection functions, and higher-order photon rings will be computed for a broad class of spacetimes. These will be systematically compared with Kerr predictions to assess which features are distinguishable with current and upcoming observations, particularly from the next-generation EHT (ngEHT). By disentangling and characterizing the quantum, geometric, and environmental contributions to the black hole shadow, this research will generate a comprehensive catalogue of shadow signatures across theoretical models. The outcomes are expected to yield critical insights into the nature of spacetime near compact objects and inform the interpretation of high-resolution black hole images. In doing so, this work will help elevate black hole shadows to a precision probe of fundamental physics, complementing gravitational wave detections and cosmological observations in the ongoing search for a deeper understanding of gravity.