The Stack Overflow podcast is back! Listen to an interview with our new CEO.

# Questions tagged [black-holes]

A black hole is a volume from which matter cannot escape. More formally, the coordinate speed of light at the event horizon - the boundary of a black hole - is zero, as measured by a sufficiently separated observer.

538 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
80 views

### Are there any SUSY black holes in D > 5?

Quoting from arXiv:0801.3471 Asymptotically flat BPS black hole solutions are known only for $d = 4,\,5$. and I've seen this claim very timidly suggested in a couple of other places, but I couldn'...
224 views

### Komar mass for rotating black hole

I am trying to calculate the Komar conserved quantities for black hole having Killing vectors. I followed the standard procedure and calculated the Komar mass for Reissner-Nordstrom black hole (plz ...
95 views

### Black hole formation from radiation in a box

In a paper I am currently studying (here), it was assumed that a black hole can form from a pure state of radiation in a box. Abstract: INFORMATION IN BLACK HOLE RADIATION arXiv:hep-th/...
96 views

192 views

### Situation after Saini & Stojkovic's paper on unitarity in gravitational collapse and non-formation of black holes?

In their paper, Anshul Saini and Dejan Stojkovic [1] claimed that by calculations it is possible to demonstrate that in a gravitational collapse of a disk, an event horizon is never made for a far ...
88 views

### Confinement of charged tachyons in AdS spacetime

It is well known that the negative cosmological constant of AdS spacetime can act like a confining potential. That is, in contrast to asymptotically flat spacetime, in an asymptotically AdS spacetime ...
550 views

### The difference between an apparent horizon and event horizon?

I'm currently writing a project on minimal surfaces and general relativity - however I don't understand the difference between the apparent and event horizon? They ultimately both seemed to be defined ...
241 views

### Is the Casimir effect also present between two event horizons?

A follow-up to this question: Is the Casimir effect also present between two event horizons?
116 views

### Spaans, “On Quantum Contributions to Black Hole Growth”

This paper was posted to arxiv a couple of weeks ago: http://arxiv.org/abs/1309.1067 From the abstract: The effects of Wheeler's quantum foam on black hole growth are explored from an ...
134 views

### Alternate geodesic completions of a Schwarzschild black hole

The Kruskal-Szekeres solution extends the exterior Schwarzschild solution maximally, so that every geodesic not contacting a curvature singularity can be extended arbitrarily far in either direction. ...
146 views

103 views

### An apparent limitation of the simplified diagrams used to describe space-time around a black hole

If you look at a 2D representation of curved space-time around a black hole, it stretches out into an infinite tube, asymptotically approaching the Schwarzschild radius. image from sciencenews.org ...
100 views

### Tidal acceleration of a body at rest in a Schwarzchild geometry using geodesic equations

I'm self-studying the properties of a Schwarzchild geometry, with line element ds^2 = \left(1-\frac{2m}{r}\right)dt^2-\left(1-\frac{2m}{r}\right)^{-1}dr^2-r^2\left(d\theta^2 + \sin^2\theta d\phi^2\...
114 views

80 views

### Computation of Hawking radiation without explicit Hamiltonian?

I've observed that computation of Hawking radiations is mostly done without explicitly computing the Hamiltonian, which would require integration over spacetime that would seem to cause problems with ...
164 views

### What is the density profile of Sagittarius A*'s accretion disk?

It is thought that Sagittarius A*, the supermassive black hole at the center of the Milky Way, is surrounded by an accretion disk. Can anyone provide a resource for the general density profile of ...
102 views

### black hole oscillations

I have several questions relating to black hole oscillations. Assume throughout what I describe are the reports of an observer outside the event horizon who is not falling into the black hole. (If ...
57 views

### Connections between Lindblad equation and black holes

There have been some investigations about wave function collapse caused by gravitation. And as is known, Lindblad equation can be regarded as a formal description of stochastic collapse of wave ...
67 views

### Vibrational modes of a black hole's event horizon

I understand that it is possible for the event horizon of a black hole to support damped modes of vibration called quasi-normal modes, in which it oscillates between spherical and and various oblate ...
105 views

### Is there a correlation between a galaxy's rotation curve and the characteristics of its black hole?

Do galaxies with larger mass black holes have different galaxy rotation curves than those with smaller black holes? What about other characteristics, such as whether they are spinning or dormant etc?
41 views

### Must collapse to a singularity proceed through a strong curvature singularity?

A strong curvature singularity (s.c.s.) can be defined as one for which a geodesic is incomplete at affine parameter $\lambda=0$, with $\lim_{\lambda\rightarrow0}\lambda^2R_{ab}v^av^b\ne0$, where $v^a$...
167 views

### Does the event horizon of a black hole need to be an oblate sphere?

Suppose two black holes where rotating around each other, perhaps spinning into each other, at a distance such that their event horizons merge into one event horizon. It seems to me that the event ...
148 views

### Limit to the Oberth effect in a supermassive Black Hole flyby

To make this question clear, here are the details of the situation I wish to entertain. A spacecraft does a powered gravitational assist, where it fires engines in a near-approach to the body We ...
108 views

### Can apparent horizons be nested?

I know that absolute event horizons are complicated and depend on the details of the metric because of their teleological nature. But I assume that an isolated gravitational singularity of mass $M$ ...
197 views

### Does Kerr metric have Hawking temperature?

Does Kerr metric with zero charge have Hawking temperature? What is it given by? I am reading a paper about and it says that the Einstein-Maxwell-Dilaton-Axion black hole and it says that temperature ...
136 views

### Showing that black holes are affected by gravity

We know from numerical simulations that black holes behave like regular objects in the sense that they are affected by gravity: they can attract and orbit each other, for example. This sounds pretty ...
431 views

### Mechanism for collapse of iron stars into black holes via quantum tunnelling

In the wikipedia page "Future of an expanding universe" it refers to the scenario of a future without proton decay. The page talks about how processes would lead to stellar-mass cold spheres of iron, ...