The term black hole
encapsulates two different concepts:
- a black hole in mathematics is an exact solution to the Einstein equations;
- a black hole in astrophysics is something astronomers "observe", which we then attempt to model using the concept of mathematical black holes.
There is an important question of principle that is often overlooked, namely:
"What features of mathematical black holes are artifacts of the mathematical idealizations, and which features are truly generic, independent of the precise mathematical idealizations?"
"It is only the generic properties that we expect to be of relevance to real astrophysical black holes. For instance, it is now known that the existence of an event horizon is generic, independent of idealizations such as spherical symmetry and time-independence, and so physically relevant to a broad class of astrophysical black holes. In contrast, the maximal extension of the Schwarzschild geometry (the Kruskal manifold) is a solely a mathematical idealization that is not physically relevant to astrophysical black holes.
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Black Holes at Victoria University of Wellington
One research theme at the Victoria University Gravity Group is the investigation of these questions of genericity.
Two main routes of attack are:
- "Dirty" black holes: Which mathematical properties of idealized black holes survive when a black hole is surrounded by arbitrary (time-independent) dirt?
The simplest form of "dirt" is an electromagnetic field, with a dilaton field as the next simplest example. But for arbitrary dirt some of the standard properties of idealized black holes still survive. This idea has been explored in a series of seven papers listed below.
- Analogue Models: Briefly, one of their key features is that analogue black holes force you to think carefully about how much of black hole physics depends specifically on the Einstein equations, and how much is "merely" kinematics arising from the existence of a horizon in curved spacetime.
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Some references on "Dirty" black holes
For further information on "Dirty" black holes see:
- Matt Visser, Dirty black holes: Thermodynamics and horizon structure. e-Print arXiv: hep-th/9203057, Physical Review D46(1992) 2445--2451
- Matt Visser, Dirty black holes: Entropy versus area. e-Print arXiv: hep-th/9303029, Physical Review D48 (1993) 583--591
- Matt Visser, Dirty black holes: Entropy as a surface term. e-Print arXiv: hep-th/9307194, Physical Review D48 (1993) 5697--5705
- Damien Martin, Joey Medved, and Matt Visser, Dirty black holes: Quasinormal modes. e-Print arXiv: gr-qc/0310009, Classical and Quantum Gravity 21 (2004) 1393--1405.
- Damien Martin, Joey Medved, and Matt Visser, Dirty black holes: Quasinormal modes for "squeezed" horizons. e-Print arXiv: gr-qc/0310097, Classical and Quantum Gravity 21 (2004) 2393--2405.
- Damien Martin, Joey Medved, and Matt Visser, Dirty black holes: Spacetime geometry and near-horizon symmetries. e-Print arXiv: gr-qc/0402069, Classical and Quantum Gravity 21 (2004) 3111-3126.
- Damien Martin, Joey Medved, and Matt Visser, Dirty black holes: Symmetries at stationary non-static horizons. e-Print arXiv: gr-qc/0403026, Physical Review D70 (2004) 024009.
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