ORCID Profile
0000-0001-7296-0420
Current Organisations
Macquarie University
,
Okinawa Institute of Science and Technology Graduate University
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Publisher: World Scientific Pub Co Pte Ltd
Date: 25-07-2023
DOI: 10.1142/S0218271823420129
Abstract: Black holes play a pivotal role in the foundations of physics, but there is an alarming discrepancy between what is considered to be a black hole in observational astronomy and theoretical studies. Despite claims to the contrary, we argue that identifying the observed astrophysical black hole candidates as genuine black holes is not justified based on the currently available observational data, and elaborate on the necessary evidence required to support such a remarkable claim. In addition, we investigate whether the predictions of semiclassical gravity are equally compatible with competing theoretical models, and find that semiclassical arguments favor horizonless configurations.
Publisher: American Physical Society (APS)
Date: 26-09-2019
Publisher: American Physical Society (APS)
Date: 16-06-2022
Publisher: WORLD SCIENTIFIC
Date: 24-01-2023
Publisher: American Physical Society (APS)
Date: 22-02-2022
Publisher: American Physical Society (APS)
Date: 30-03-2021
Publisher: World Scientific Pub Co Pte Ltd
Date: 04-06-2022
DOI: 10.1142/S0218271822300154
Abstract: For distant observers, black holes are trapped spacetime domains bounded by apparent horizons. We review properties of the near-horizon geometry emphasizing the consequences of two common implicit assumptions of semiclassical physics. The first is a consequence of the cosmic censorship conjecture, namely, that curvature scalars are finite at apparent horizons. The second is that horizons form in finite asymptotic time (i.e. according to distant observers), a property implicitly assumed in conventional descriptions of black hole formation and evaporation. Taking these as the only requirements within the semiclassical framework, we find that in spherical symmetry only two classes of dynamic solutions are admissible, both describing evaporating black holes and expanding white holes. We review their properties and present the implications. The null energy condition is violated in the vicinity of the outer horizon and satisfied in the vicinity of the inner apparent/anti-trapping horizon. Apparent and anti-trapping horizons are timelike surfaces of intermediately singular behavior, which manifests itself in negative energy density firewalls. These and other properties are also present in axially symmetric solutions. Different generalizations of surface gravity to dynamic spacetimes are discordant and do not match the semiclassical results. We conclude by discussing signatures of these models and implications for the identification of observed ultra-compact objects.
Publisher: WORLD SCIENTIFIC
Date: 24-01-2023
Publisher: American Vacuum Society
Date: 03-2022
DOI: 10.1116/5.0073598
Abstract: In spherical symmetry, solutions of the semiclassical Einstein equations belong to one of two possible classes. Both classes contain solutions that—depending on the dynamic behavior of the horizon—describe evaporating physical black holes or expanding white holes (trapped/anti-trapped regions that form in finite time of a distant observer). These solutions are real-valued only if the null energy condition (NEC) is violated in the vicinity of the Schwarzschild sphere. We review their properties and describe the only consistent black hole formation scenario. While the curvature scalars are finite on the outer apparent/anti-trapping horizon, it is still a weakly singular surface. This singularity manifests itself in a mild firewall. Near the inner apparent horizon, the NEC is satisfied. Models of static regular black holes are known to be unstable, but since dynamic models of regular black holes are severely constrained by self-consistency requirements, their stability requires further investigation.
Publisher: American Physical Society (APS)
Date: 08-2023
Publisher: American Physical Society (APS)
Date: 20-09-2021
Publisher: American Physical Society (APS)
Date: 11-06-2019
Location: No location found
Location: Japan
No related grants have been discovered for Sebastian Murk.