Questions around Black Holes

[geordief]

For a physical black hole one would expect fields and particles to be inside the horizon.

Would they exert pressure on each other , so that we could think about them as some kind of a pressure cooker?

 

(from your answer, Iit seems my idea (well I did hear it from somewhere else that a BH was simply a deformation in SpaceTime was wrong)

[ajb]

Would they exert pressure on each other , so that we could think about them as some kind of a pressure cooker?

I don't know, or really I am not sure what one means by that.

[geordief]

I don't know, or really I am not sure what one means by that.

Well the reason I asked is that I had heard many times that there is nothing to prevent the BH collapsing on itself into the singularity (I don't take "singularity" to have any defined meaning) and so I wondered if the objects inside the BH would somehow prevent an uncontrolled collapse by virtue of their increasing density.

 

Is there really nothing in the particles (also what kinds of fields are there?) to counteract the pull towards the "centre".

 

And do the particles/fields exert a gravitational force on each other? Or do they not continue to deform space time in a decentralized way so that some particles are actually being pulled up towards the event horizon even if they cannot escape it?

[ajb]

Well the reason I asked is that I had heard many times that there is nothing to prevent the BH collapsing on itself into the singularity...

I am not sure what you mean by a black hole collapsing. A black hole solution in general relativity is a vacuum solution - there is nothing to actually collapse. The additional fields and particles are are uasually thought of as test particles, meaning that they don't contribute to the geometry/gravity.

 

 

...and so I wondered if the objects inside the BH would somehow prevent an uncontrolled collapse by virtue of their increasing density.

Test particles will hit the singularity - at least classically.

 

Is there really nothing in the particles (also what kinds of fields are there?) to counteract the pull towards the "centre".

Not for test particles - if you had enough mass inside the horizon then it may not be a black hole solution. For example, the Schwarzschild works fine for the external space-time of say the Sun. There is no horizon here as it would sit inside the Sun, but in that region we do not have a vacuum solution, thus we need some other solution to the field equations - so called interior solutions..

 

And do the particles/fields exert a gravitational force on each other? Or do they not continue to deform space time in a decentralized way so that some particles are actually being pulled up towards the event horizon even if they cannot escape it?

Usually we treat them as only being acted on by gravity and not creating any gravity. But this is an approximantion that is thought to be okay.

[geordief]

thanks. I will need to look into that