I am a theoretical physicist trying to uncover the fundamental nature of our reality. My research interests center around black holes, holography, and novel applications of deep learning algorithms to problems in physics. I am especially interested in understanding how classical spacetime might emerge from quantum field theory correlation functions, in a setting where information constitutes the elemental building blocks of the Universe.
Can we understand black holes as ordinary thermodynamic systems? General relativity describes black holes not as corporeal objects, but geometric features of spacetime itself. Yet they seem to possess properties like temperature and entropy, which we normally attribute to ordinary objects made of atoms. I am interested in understanding to what extent black holes can be described as thermodynamic systems, and what can be revealed about their microscopic structure as a result.
Is the Universe a hologram? This possibility arises from a general feature of gauge theories; that symmetries which are trivial in the bulk can become physical in the presence of a boundary. This fact underlies numerous examples of holography---the description of a bulk gravitational system purely in terms of non-gravitating degrees of freedom on an appropriate lower-dimensional boundary. I am trying to understand the role that black holes play in this picture. They are known to be dual to thermal states in the boundary conformal field theory, however the rich landscape of thermodynamic phenomena exhibited by black holes still remains largely unexplored in the dual. Understanding these duals will be important for finding practical applications of holography to condensed matter systems.
Quantum fields exhibit remarkable properties in the presence of strong gravity. I am working on developing sophisticated new semi-classical models of black holes, and finding new signatures of quantum effects which may alter their structure. Significant advancements in gravitational wave astronomy are rapidly enabling the imaging of black holes at the horizon scale, and understanding how their features manifest in gravitational wave signals will be a crucial part of upcoming observational efforts. I am especially interested in how quasinormal oscillations are affected by semi-classical effects near the horizon, and whether such effects can imprint themselves on gravitational waves.
Abstract:
We compute quasinormal mode frequencies for static limits of physical black holes - semi-classical black hole solutions to Einstein-Hilbert gravity characterized by the finite formation time of an apparent horizon and its weak regularity. Using a two-point M-fraction approximation to construct an interpolating metric which captures the essential near-horizon and asymptotic properties of black holes, we explore a large part of the parameter space that characterizes the near-horizon geometry. We cast the problem as a discretized homogeneous eigensystem and compute the low-lying quasinormal mode frequencies for perturbations of a massless scalar field.
Abstract:
We study various aspects of modeling astrophysical black holes using the recently introduced semiclassical formalism of physical black holes (PBHs). This approach is based on the minimal requirements of observability and regularity of the horizons. We demonstrate that PBHs do not directly couple to the cosmological background in the current epoch, and their equation of state renders them unsuitable for describing dark energy. Utilizing their properties for analysis of more exotic models, we present a consistent semiclassical scenario for a black-to-white hole bounce and identify obstacles to the transformation from a black hole horizon to a wormhole mouth.
Abstract:
We trace the origins and development of black hole thermodynamics across the past half-century, emphasizing the framework's relation to classical thermodynamics, and the vital role played by the notions of equilibrium, stationarity, and symmetry. We discuss different interpretations of the first law of black hole mechanics, and assess the validity of its mechanical, process-based interpretation for evaporating black holes. We bring these ideas to the cosmological realm, and highlight the various difficulties that arise when formulating thermodynamics for black holes in asymptotically de Sitter backgrounds. We discuss a number of proposed solutions and the open questions that arise therein.
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