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Author Topic:   Did a 5-D black hole brane event horizon make the universe?
Son Goku
Inactive Member


(1)
Message 3 of 18 (711132)
11-15-2013 10:15 AM


5D Black Holes
I read the paper. It's actually a cool idea. Basically they studied in detail the dynamics of what happens when very heavy stars collapse to form black holes in a universe with four dimensions*.
In three-dimensions, when a star collapses, the outer layers get blown out into space and the inner layers collapse to form a black hole. The black hole being surrounded by the two-dimensional surface know as the event horizon. The surface past which light cannot escape.
However the authors have found that this isn't what happens in four-dimensions. The inner layers collapse into a black hole and are surrounded by a three-dimensional event horizon. However all of the outer layers don't explode out randomly into space like they do in three dimensions.
Some of the outer layers form a thin-sheet, a three dimensional sheet, that looks like an extra layer on top of the event horizon. This sheet then expands slowly away from the star, as it has enough momentum to escape the collapse.
It turns out that this sheet, when taken as an object on its own, is identical to the Big Bang solution of General Relativity in three-dimensions. So an entity living on this sheet would see data consistent with there being no fourth dimension and everything originating from a point in the distant past.
Usually the singularity in General Relativity is taken to mean some approximation or assumption is breaking down. This model would say that as we rewind time we eventually reach a point before the star collapsed and our universe merges with the other layers of the star and can no longer be considered an independent object.
In essence, this model says our universe is "really" a slowly expanding bubble of stellar material, one of the mid layers of a hyperstar** that went supernova. The gravity of the black hole that that star collapsed into keeps the layer compressed and effectively three-dimensional, but the energy of the supernova blast gives it enough velocity to slowly escape from the black hole and so it expands. Living inside this sheet, we perceive this expansion as the cosmological expansion of a three-dimensional universe.
I think the idea is in too early a stage to comment on. The author wants to do better simulations to see if it matches current cosmological data. The model currently matches some observations, but the three-dimensional universe this model produces is scale invariant. Basically its Cosmic Microwave Background (CMB) has an equal number of photons of each energy. Where as our universe shows slightly more photons at some energies.
However it's possible this model does produce a universe like ours, but the current methods of analyzing it are too weak to demonstrate this, or perhaps depending on the conditions in the hyperstar the three-dimensional universe has different CMBs.
*I'm ignoring time in this post.
**Hyperstar refers to the four-dimensional star.
Edited by Son Goku, : No reason given.

Replies to this message:
 Message 4 by AZPaul3, posted 11-15-2013 3:02 PM Son Goku has replied

  
Son Goku
Inactive Member


(2)
Message 5 of 18 (711238)
11-16-2013 8:52 AM
Reply to: Message 4 by AZPaul3
11-15-2013 3:02 PM


Re: 5D Black Holes
Well the interesting thing is that accelerating expansion and Dark Energy naturally fall out of the model.
Our universe, which according to this is simply a "sphere" of material slowly escaping from a dead hyperstar's black hole, has its size increase as it escapes the black hole.
The interesting thing is that this expansion naturally accelerates. The basic laws of physics in the higher dimensional universe dictate that a spherical shock wave of material accelerates as it moves away from the black hole.
To beings living inside the shock wave (i.e. us), the only way they could model this expansion without reference to the higher dimensions is by introducing an additional Dark Energy term into General Relativity.
In essence in this model, there is no mechanism for the accelerating expansion besides basic kinematics. Spherical shells of supernova debris simply naturally accelerate away from a four-dimensional black hole.
Edited by Son Goku, : No reason given.
Edited by Son Goku, : No reason given.

This message is a reply to:
 Message 4 by AZPaul3, posted 11-15-2013 3:02 PM AZPaul3 has seen this message but not replied

Replies to this message:
 Message 6 by Diomedes, posted 11-18-2013 10:25 AM Son Goku has replied

  
Son Goku
Inactive Member


Message 7 of 18 (711478)
11-19-2013 11:45 AM
Reply to: Message 6 by Diomedes
11-18-2013 10:25 AM


Re: 5D Black Holes
I am curious: does this imply that our universe is, in and of itself, a 'bubble' within another four dimensional universe of some type?
If his theory is correct, then yes that is exactly what it implies.
I should say that what interests me most here is that the author derived explicit predictions from his model. Things we can check over the next few years. Unlike a lot of models which try to explain the Big Bang which often simply paint some vague idea with some mathematics without any solid predictions.
I'm also a little confused with regards to three dimensional universes versus four dimensional universes. Is the 'fourth dimension', as implied in this case, not the dimension of time but something else?
It's an extra spatial dimension.
And a final question: since space-time is a fundamental construct of our universe, isn't our universe already a four dimensional universe?
In my post I said that I wouldn't include time, as it wasn't necessary to understand this model. However correctly our universe is 3+1-dimensional. This model says we might be a bubble in a 4+1 dimensional universe.
The 3+1 notation is often used to indicate that we have four dimensions but one of them is different to the others.

This message is a reply to:
 Message 6 by Diomedes, posted 11-18-2013 10:25 AM Diomedes has replied

Replies to this message:
 Message 8 by Diomedes, posted 11-19-2013 12:08 PM Son Goku has not replied

  
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