PhD. Thesis Defense: Elham Ghorani
Black Hole Solutions in Extended Metric-Palatini Gravity
Elham Ghorani
Physics, PhD Dissertation, 2025
Thesis Jury
Prof. Dr. Mehmet Zafer Gedik (Thesis Advisor)
Dr. Beyhan Puliçe (Thesis Co-advisor)
Prof. Dr. Ersin Göğüş
Assoc. Prof. Göktuğ Karpat
Prof. Dr. Tonguç Rador
Prof. Dr. Kazım Yavuz Ekşi
Date & Time: 16th July, 2025 – 12:30 PM
Place: FASS G049
Zoom Link: https://sabanciuniv.zoom.us/j/
Keywords : General Relativity, Palatini Gravity ,Geometric Proca, Black Hole Solutions
Abstract
Extended metric-Palatini gravity, quadratic in the antisymmetric part of the affine curvature, is known to lead to the general relativity plus a geometric Proca field. The geometric Proca, equivalent of the non-metricity vector in the torsion-free affine connection, qualifies to be a distinctive signature of the affine curvature. In this thesis, we explore how photon and particle motion near black holes can be used to probe the geometric Proca field. To this end, we derive static spherically symmetric field equations of this Einstein-geometric Proca theory, and show that it admits black hole solutions in asymptotically AdS background. We perform a detailed study of the optical properties and shadow of this black hole and contrast them with the observational data by considering black hole environments with and without plasma. As a useful astrophysical application, we discuss constraints on the Proca field parameters using the observed angular size of the shadow of supermassive black holes M87∗ and Sgr A∗ in both vacuum and plasma cases. We then perform a detailed analysis using the observational quasiperiodic oscillations (QPOs) data. We use the latest data from stellar-mass black hole GRO J1655-40, intermediatemass black hole in M82-X1, and the super-massive black hole in SgA* (our Milky Way) and perform a Monte-Carlo-Markov-Chain (MCMC) analysis to determine or bound the model parameters. Our results shed light on the allowed ranges of the Proca mass and other parameters. The results imply that our solutions can cover all three astrophysical black holes. Overall, we find that the geometric Proca can be probed via the black hole observations. Our analysis can also be extended to more general metric-affine gravity theories.