*Ta-Pei Cheng*

- Published in print:
- 2009
- Published Online:
- February 2010
- ISBN:
- 9780199573639
- eISBN:
- 9780191722448
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199573639.003.0008
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology

Black hole is an object so compact that it is inside its event horizon: a one-way surface through which particle and light can only traverse inward, and an exterior observer cannot receive any signal ...
More

Black hole is an object so compact that it is inside its event horizon: a one-way surface through which particle and light can only traverse inward, and an exterior observer cannot receive any signal sent from inside. The Schwarzschild geometry is viewed in the Eddington-Finkelstein coordinates as well as in the Kruskal coordinates. Besides a black hole, the GR field equation also allows the solution of a white hole and a wormhole. The gravitational energy released when a particle falls into a tightly bound orbit around a black hole can be enormous. The physical reality of, and observational evidence for, black holes are briefly discussed. Quantum fluctuation around the event horizon brings about the Hawking radiation. This and the Penrose process in a rotating (Kerr) black hole comes about because of the possibility of negative energy particles falling into a black hole.Less

Black hole is an object so compact that it is inside its event horizon: a one-way surface through which particle and light can only traverse inward, and an exterior observer cannot receive any signal sent from inside. The Schwarzschild geometry is viewed in the Eddington-Finkelstein coordinates as well as in the Kruskal coordinates. Besides a black hole, the GR field equation also allows the solution of a white hole and a wormhole. The gravitational energy released when a particle falls into a tightly bound orbit around a black hole can be enormous. The physical reality of, and observational evidence for, black holes are briefly discussed. Quantum fluctuation around the event horizon brings about the Hawking radiation. This and the Penrose process in a rotating (Kerr) black hole comes about because of the possibility of negative energy particles falling into a black hole.

*Nathalie Deruelle and Jean-Philippe Uzan*

- Published in print:
- 2018
- Published Online:
- October 2018
- ISBN:
- 9780198786399
- eISBN:
- 9780191828669
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198786399.003.0049
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology

This chapter describes two physical processes related to the Schwarzschild and Kerr solutions which can be induced by the gravitational field of a black hole. The first is the Penrose process, which ...
More

This chapter describes two physical processes related to the Schwarzschild and Kerr solutions which can be induced by the gravitational field of a black hole. The first is the Penrose process, which suggests that rotating black holes are large energy reservoirs. Next is superradiance, which is the first step in the study of black-hole stability. The study of the stability of black holes involves the linearization of the Einstein equations about the Schwarzschild or Kerr solution. As this chapter shows, the equations of motion for perturbations of the metric are wave equations. The problem then is to determine whether or not these solutions are bounded.Less

This chapter describes two physical processes related to the Schwarzschild and Kerr solutions which can be induced by the gravitational field of a black hole. The first is the Penrose process, which suggests that rotating black holes are large energy reservoirs. Next is superradiance, which is the first step in the study of black-hole stability. The study of the stability of black holes involves the linearization of the Einstein equations about the Schwarzschild or Kerr solution. As this chapter shows, the equations of motion for perturbations of the metric are wave equations. The problem then is to determine whether or not these solutions are bounded.

*Andrew M. Steane*

- Published in print:
- 2016
- Published Online:
- January 2017
- ISBN:
- 9780198788560
- eISBN:
- 9780191830426
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198788560.003.0026
- Subject:
- Physics, Theoretical, Computational, and Statistical Physics

The basic thermodynamics of self-gravitating systems is explained. First the virial theorem is introduced, and it is shown that a gravitating cloud bound by its own gravity is unstable, and each ...
More

The basic thermodynamics of self-gravitating systems is explained. First the virial theorem is introduced, and it is shown that a gravitating cloud bound by its own gravity is unstable, and each region of such a cloud has a negative heat capacity. The Jean’s length is obtained by a simple argument. Black holes and Hawking radiation are discussed. The area theorem and Penrose process are sketched, and the formulae for temperature and entropy of a black hole are given. Black hole evaporation is described.Less

The basic thermodynamics of self-gravitating systems is explained. First the virial theorem is introduced, and it is shown that a gravitating cloud bound by its own gravity is unstable, and each region of such a cloud has a negative heat capacity. The Jean’s length is obtained by a simple argument. Black holes and Hawking radiation are discussed. The area theorem and Penrose process are sketched, and the formulae for temperature and entropy of a black hole are given. Black hole evaporation is described.