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Exotic encounters: Buchdahl's conditions and physical black holes.

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Bibliographic Details
Title: Exotic encounters: Buchdahl's conditions and physical black holes.
Authors: Soranidis, Ioannis1 (AUTHOR) ioannis.soranidis@mq.edu.au, Terno, Daniel R.1 (AUTHOR) daniel.terno@mq.edu.au
Source: International Journal of Modern Physics D: Gravitation, Astrophysics & Cosmology. Dec2025, Vol. 34 Issue 16, p1-9. 9p.
Subject Terms: *BLACK holes, *COMPACT objects (Astronomy), *PROPERTIES of matter, *ASTROPHYSICS
Abstract: Black holes are among the most well-known astrophysical objects, yet their physical realisation remains conceptually subtle. We analyse physical black holes — light-trapping regions that form in finite time as seen by a distant observer — and investigate the properties of the matter required to support them. Taking Buchdahl's theorem as a benchmark, we show that these configurations necessarily violate at least two of its four original conditions, and the post-formation state violates them all. These violations are substantial: They include the null energy condition, nonmonotonic energy profiles, and strong pressure anisotropies. Thus, the requirement of truly forming horizon places physical black holes in a class of solutions that are more exotic than exotic compact objects. [ABSTRACT FROM AUTHOR]
Database: Academic Search Index
Description
Abstract:Black holes are among the most well-known astrophysical objects, yet their physical realisation remains conceptually subtle. We analyse physical black holes — light-trapping regions that form in finite time as seen by a distant observer — and investigate the properties of the matter required to support them. Taking Buchdahl's theorem as a benchmark, we show that these configurations necessarily violate at least two of its four original conditions, and the post-formation state violates them all. These violations are substantial: They include the null energy condition, nonmonotonic energy profiles, and strong pressure anisotropies. Thus, the requirement of truly forming horizon places physical black holes in a class of solutions that are more exotic than exotic compact objects. [ABSTRACT FROM AUTHOR]
ISSN:02182718
DOI:10.1142/S0218271825440134