{"id":{"repo_id":"cagliari","oai_identifier":"oai:iris.unica.it:11584/437425"},"canonical_url":"https://search.dev.ndltd.org/etd/cagliari/oai:iris.unica.it:11584/437425","repository":{"repo_id":"cagliari","name":"Università di Cagliari","base_url":"https://iris.unica.it/oai/request"},"display":{"title":"Quantum Corrected and Nonsingular Black Holes: Theoretical and Phenomenological Aspects","abstract":"General Relativity is a cornerstone of modern physics and has now achieved the status of precision science. Despite its success in explaining a wide range of phenomena, significant open questions remain about the fundamental nature of gravity. These unresolved issues suggest the need for a quantum extension of Einstein's theory, which has remained elusive until now. \\\\ This thesis explores various instances of quantum-gravity effects in different setups, focusing on their impact on the structure of black-hole horizons, spacetime singularities and the observable phenomenology. A quantum-corrected BTZ black hole constructed on a brane in AdS4 spacetime is first examined, providing evidence that these quantum effects strengthen the weak cosmic censorship, thereby enhancing the stability of the black-hole horizon. Subsequently, the spacetime geometry generated by a point-like source in a superposition of different locations is considered. It is shown that the quantum corrections, induced by the position uncertainty, excise the conventional Schwarzschild singularity and generate a regular geometry interpolating between a nonsingular black hole and a traversable wormhole. Furthermore, a broad class of de-Sitter-core nonsingular black-hole models is constructed, which are sourced by an anisotropic fluid, assumed to encode quantum-gravity corrections. It is shown that these solutions have several interesting features: presence of an additional and possibly super-planckian \"quantum” hair, a regular, extremal black-hole state and a thermodynamic phase transition favoring black holes with super-planckian hairs. A two-dimensional model of a regular black hole retaining these features is then used to address the information loss issue: the evaporation process at semiclassical level is examined, including backreaction effects. It is found that the radiation entanglement entropy decreases after reaching a maximum and that the endpoint of the evaporation is a regular, zero-entropy state. This suggests a profound (and often overlooked) connection between the resolution of singularities and the information problem. Some new regular solutions of Einstein-scalar gravity in four dimensions are also analyzed, formulating and extending no-go theorems on their existence. Additionally, certain unstable, regular, horizonless scalar solutions are identified that describe the nucleation of a dS4 out of an AdS4 spacetime in the UV regime, with potential implications for characterizing string-theory vacua and cosmological inflation. Finally, on the phenomenological side, a way to constrain the strength of quantum-gravity corrections using data from the S2 star orbit around SgrA* is explored. Additionally, another novel approach to test the regular-black-hole paradigm is proposed, which is based on a nontrivial coupling of nonsingular black holes with the large-scale cosmological dynamics. Although observational evidence for this effect remains contentious and debated, confirmation of such coupling would provide compelling evidence for the nonsingular nature of black holes.","abstract_html":"General Relativity is a cornerstone of modern physics and has now achieved the status of precision science. Despite its success in explaining a wide range of phenomena, significant open questions remain about the fundamental nature of gravity. These unresolved issues suggest the need for a quantum extension of Einstein's theory, which has remained elusive until now. \\\\ This thesis explores various instances of quantum-gravity effects in different setups, focusing on their impact on the structure of black-hole horizons, spacetime singularities and the observable phenomenology. A quantum-corrected BTZ black hole constructed on a brane in AdS4 spacetime is first examined, providing evidence that these quantum effects strengthen the weak cosmic censorship, thereby enhancing the stability of the black-hole horizon. Subsequently, the spacetime geometry generated by a point-like source in a superposition of different locations is considered. It is shown that the quantum corrections, induced by the position uncertainty, excise the conventional Schwarzschild singularity and generate a regular geometry interpolating between a nonsingular black hole and a traversable wormhole. Furthermore, a broad class of de-Sitter-core nonsingular black-hole models is constructed, which are sourced by an anisotropic fluid, assumed to encode quantum-gravity corrections. It is shown that these solutions have several interesting features: presence of an additional and possibly super-planckian "quantum” hair, a regular, extremal black-hole state and a thermodynamic phase transition favoring black holes with super-planckian hairs. A two-dimensional model of a regular black hole retaining these features is then used to address the information loss issue: the evaporation process at semiclassical level is examined, including backreaction effects. It is found that the radiation entanglement entropy decreases after reaching a maximum and that the endpoint of the evaporation is a regular, zero-entropy state. This suggests a profound (and often overlooked) connection between the resolution of singularities and the information problem. Some new regular solutions of Einstein-scalar gravity in four dimensions are also analyzed, formulating and extending no-go theorems on their existence. Additionally, certain unstable, regular, horizonless scalar solutions are identified that describe the nucleation of a dS4 out of an AdS4 spacetime in the UV regime, with potential implications for characterizing string-theory vacua and cosmological inflation. Finally, on the phenomenological side, a way to constrain the strength of quantum-gravity corrections using data from the S2 star orbit around SgrA* is explored. Additionally, another novel approach to test the regular-black-hole paradigm is proposed, which is based on a nontrivial coupling of nonsingular black holes with the large-scale cosmological dynamics. Although observational evidence for this effect remains contentious and debated, confirmation of such coupling would provide compelling evidence for the nonsingular nature of black holes.","abstract_has_math":false,"creators":["SANNA, ANDREA PIERFRANCESCO"],"institution":"Università degli Studi di Cagliari","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["CADONI, MARIANO"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-01-31T00:00:00+01:00","date_published":"2025-01-31T00:00:00+01:00","updated_at":"2026-07-24T01:29:55Z","subjects":["Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici"],"languages":["eng"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/11584/437425","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["CADONI, MARIANO"]},{"key":"dc:creator","label":"Author","values":["SANNA, ANDREA PIERFRANCESCO"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-01-31T00:00:00+01:00"]},{"key":"dc:publisher","label":"Institution","values":["Università degli Studi di Cagliari"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/11584/437425"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["General Relativity is a cornerstone of modern physics and has now achieved the status of precision science. Despite its success in explaining a wide range of phenomena, significant open questions remain about the fundamental nature of gravity. These unresolved issues suggest the need for a quantum extension of Einstein's theory, which has remained elusive until now. \\\\ This thesis explores various instances of quantum-gravity effects in different setups, focusing on their impact on the structure of black-hole horizons, spacetime singularities and the observable phenomenology. A quantum-corrected BTZ black hole constructed on a brane in AdS4 spacetime is first examined, providing evidence that these quantum effects strengthen the weak cosmic censorship, thereby enhancing the stability of the black-hole horizon. Subsequently, the spacetime geometry generated by a point-like source in a superposition of different locations is considered. It is shown that the quantum corrections, induced by the position uncertainty, excise the conventional Schwarzschild singularity and generate a regular geometry interpolating between a nonsingular black hole and a traversable wormhole. Furthermore, a broad class of de-Sitter-core nonsingular black-hole models is constructed, which are sourced by an anisotropic fluid, assumed to encode quantum-gravity corrections. It is shown that these solutions have several interesting features: presence of an additional and possibly super-planckian \"quantum” hair, a regular, extremal black-hole state and a thermodynamic phase transition favoring black holes with super-planckian hairs. A two-dimensional model of a regular black hole retaining these features is then used to address the information loss issue: the evaporation process at semiclassical level is examined, including backreaction effects. It is found that the radiation entanglement entropy decreases after reaching a maximum and that the endpoint of the evaporation is a regular, zero-entropy state. This suggests a profound (and often overlooked) connection between the resolution of singularities and the information problem. Some new regular solutions of Einstein-scalar gravity in four dimensions are also analyzed, formulating and extending no-go theorems on their existence. Additionally, certain unstable, regular, horizonless scalar solutions are identified that describe the nucleation of a dS4 out of an AdS4 spacetime in the UV regime, with potential implications for characterizing string-theory vacua and cosmological inflation. Finally, on the phenomenological side, a way to constrain the strength of quantum-gravity corrections using data from the S2 star orbit around SgrA* is explored. Additionally, another novel approach to test the regular-black-hole paradigm is proposed, which is based on a nontrivial coupling of nonsingular black holes with the large-scale cosmological dynamics. Although observational evidence for this effect remains contentious and debated, confirmation of such coupling would provide compelling evidence for the nonsingular nature of black holes."]},{"key":"dc:title","label":"Title","values":["Quantum Corrected and Nonsingular Black Holes: Theoretical and Phenomenological Aspects"]}]}],"canonical_facts":{"dc:contributor":["CADONI, MARIANO"],"dc:creator":["SANNA, ANDREA PIERFRANCESCO"],"dc:date":["2025-01-31T00:00:00+01:00"],"dc:description":["General Relativity is a cornerstone of modern physics and has now achieved the status of precision science. Despite its success in explaining a wide range of phenomena, significant open questions remain about the fundamental nature of gravity. These unresolved issues suggest the need for a quantum extension of Einstein's theory, which has remained elusive until now. \\\\ This thesis explores various instances of quantum-gravity effects in different setups, focusing on their impact on the structure of black-hole horizons, spacetime singularities and the observable phenomenology. A quantum-corrected BTZ black hole constructed on a brane in AdS4 spacetime is first examined, providing evidence that these quantum effects strengthen the weak cosmic censorship, thereby enhancing the stability of the black-hole horizon. Subsequently, the spacetime geometry generated by a point-like source in a superposition of different locations is considered. It is shown that the quantum corrections, induced by the position uncertainty, excise the conventional Schwarzschild singularity and generate a regular geometry interpolating between a nonsingular black hole and a traversable wormhole. Furthermore, a broad class of de-Sitter-core nonsingular black-hole models is constructed, which are sourced by an anisotropic fluid, assumed to encode quantum-gravity corrections. It is shown that these solutions have several interesting features: presence of an additional and possibly super-planckian \"quantum” hair, a regular, extremal black-hole state and a thermodynamic phase transition favoring black holes with super-planckian hairs. A two-dimensional model of a regular black hole retaining these features is then used to address the information loss issue: the evaporation process at semiclassical level is examined, including backreaction effects. It is found that the radiation entanglement entropy decreases after reaching a maximum and that the endpoint of the evaporation is a regular, zero-entropy state. This suggests a profound (and often overlooked) connection between the resolution of singularities and the information problem. Some new regular solutions of Einstein-scalar gravity in four dimensions are also analyzed, formulating and extending no-go theorems on their existence. Additionally, certain unstable, regular, horizonless scalar solutions are identified that describe the nucleation of a dS4 out of an AdS4 spacetime in the UV regime, with potential implications for characterizing string-theory vacua and cosmological inflation. Finally, on the phenomenological side, a way to constrain the strength of quantum-gravity corrections using data from the S2 star orbit around SgrA* is explored. Additionally, another novel approach to test the regular-black-hole paradigm is proposed, which is based on a nontrivial coupling of nonsingular black holes with the large-scale cosmological dynamics. Although observational evidence for this effect remains contentious and debated, confirmation of such coupling would provide compelling evidence for the nonsingular nature of black holes."],"dc:identifier":["https://hdl.handle.net/11584/437425"],"dc:language":["eng"],"dc:publisher":["Università degli Studi di Cagliari"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:subject":["Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici"],"dc:title":["Quantum Corrected and Nonsingular Black Holes: Theoretical and Phenomenological Aspects"],"dc:type":["info:eu-repo/semantics/doctoralThesis"]},"updated_at":"2026-07-24T01:29:55Z"}