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Some Cosmologists have speculated that the Universe formed from the debris ejected when a four-dimensional star collapsed into a black hole a scenario that would help to explain why the cosmos seems to be so uniform in all directions.

It is also difficult to explain how a violent Big Bang would have left behind a Universe that has an almost completely uniform temperature, because there does not seem to have been enough time since the birth of the cosmos for it to have reached temperature equilibrium.

if the bulk universe contained its own four-dimensional (4D) stars, some of them could collapse, forming 4D black holes in the same way that massive stars in our Universe do: they explode as supernovae, violently ejecting their outer layers, while their inner layers collapse into a black hole.

In our Universe, a black hole is bounded by a spherical surface called an event horizon. Whereas in ordinary three-dimensional space it takes a two-dimensional object (a surface) to create a boundary inside a black hole, in the bulk universe the event horizon of a 4D black hole would be a 3D object — a shape called a hypersphere.

When Cosmologists modeled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.

The 3D Universe we live in might be just such a brane — and that we detect the brane’s growth as cosmic expansion. “Astronomers measured that expansion and extrapolated back that the Universe must have begun with a Big Bang.

The models also naturally explains our Universe’s uniformity. Because the 4D bulk universe could have existed for an infinitely long time in the past, there would have been ample opportunity for different parts of the 4D bulk to reach an equilibrium, which our 3D Universe would have inherited.

Has this theory been tested?

Source: http://www.nature.com/news/did-a-hyper-black-hole-spawn-the-universe-1.13743

Noah
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  • I am guessing you are talking about this? http://www.nature.com/news/did-a-hyper-black-hole-spawn-the-universe-1.13743

    But even then, what is your question?

     – Secret Jul 27 '16 at 04:34
  • @Secret To me, his question looks clear, but correctly answering it would require around 20 pages even on an enthusiast level. Btw, also I have some never expiring questions. – peterh Jul 27 '16 at 04:52
  • Even if the model is correct, then I would be more interested in knowing how did the 4D universe form, from a 5D universe I guess, with no end to the series. – kpv Jul 27 '16 at 04:59
  • @kpv I suspect a simple gas cloud formed into a 4-sphere wouldn't be enough, because in this case there would be obvious signs of an underlying 4d mechanics. Some mechanism should exist which strongly fixes the particles on the plane, so strongly, that even the LHC and astronomical data could't find anything until now. And this puts the theory into the "interesting theory, no evidence" line. – peterh Jul 27 '16 at 05:05
  • @peterh the question is now clear as of the edit 29 mins ago by OP (previously there is no question). And well, most cosmology theories often end up like this , our technology still need quite a bit of time to caught up with them – Secret Jul 27 '16 at 05:07
  • @Secret Ok - ok. – peterh Jul 27 '16 at 05:08
  • Well, the Big Bang model as it has developed, explains the CMB uniformity with the inflaton field and there is nothing new or necessary offered by these speculations – anna v Jul 27 '16 at 05:08
  • @peterh: I agree, and I would like to go even a step farther. In a 3D world, there is nothing real that is 2D. All truly 2D stuff has to be imaginary. Think of a sheet of paper is not 2D. Same way, there can not be anything real 3D in a 4D world, unless it is imaginary, or virtual. There are only three spatial dimensions and that is it I suppose. – kpv Jul 27 '16 at 05:15
  • @kpv The general relativity is a geometric theory, and works very well. Thus, Occam's razor says, not only everything looks as if the spacetime would be curved, but it is really curved. And, if it is curved, then suspecting an "outer spacetime" is obvious. Now the problem is that the GR uses exclusively intrinsic parameters, which means only parameters which are measurable internally. Thus, it is theoretically impossible to know anything from the "embedding", more-dimensional space which our 3+1D spacetime is embedded in, what makes it un-physical. – peterh Jul 27 '16 at 05:30
  • @kpv Btw, on the surface of a neutron star, or even on the phase border between the two fluids in your coctail, actually a 2D physics exists with its specific laws. For a bacteria living in your coctail and if it can exist exclusively on the border, there is a 2D universe. – peterh Jul 27 '16 at 05:38
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    Models are meaningless unless one can match them to some data. We don't have data of the earliest universe. The statements we have about that, too, is just another model calculation. – CuriousOne Jul 27 '16 at 05:57
  • @peterh: I get your point from theory perspective. However from practicality point of view, however small the bacteria is, for the bacteria itself, all its dimensions are comparable in all three Ds. So, the bacteria would know it is not a 2D being. It may appear to bigger being as a 2 D but not to itself. Actually, to a very large 2D or a 3D being, it may seem to be a even a zero D being. Even smallest of the particles are not 2D in reality. – kpv Jul 27 '16 at 05:59
  • @kpv The bacteria can have experimental evidence from the 3D world, we don't have anything from a >3D world. Until now. As I know, the 10+1D (or the 25+1D) in the string theory is coming from an argument very similar to Occam's razor: it is required to null out the majority of some very complex formula :-) – peterh Jul 27 '16 at 06:13
  • @peterh: Yeah, I do not want to become a target here, but some extent of mathematical brain washing unfortunately does exist :-) – kpv Jul 27 '16 at 06:26
  • @kpv If there is, it must be coming from far higher levels as the scientists can reach, which makes it un-physical. :-) – peterh Jul 27 '16 at 07:19

1 Answers1

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Being a layman, probably better answers are also possible. Here is what I know/think.

The problem is, that there is no evidence. The LHC is actively on the search to find extra dimensions, without any result (until now).

The branes are beyond SM things, i.e. there are a lot of papers about them, but no experimental data proving or disproving them.

A theory is only acceptable, if it can predict things, and if it is falsifiable. Thus, no evidence exist against it, but it predicts experimentally verifiable things. Until that, it is only a hyphothesis. This hyperblackhole thing falls in this category, too.

There is a (not very strong) argument against it: recently the WMAP data and other experiments were used to measure the curvature of the Universe. The surprising result was that it is flat - below the measurement precision. It is a (not very strong) argument for that the Universe is infinite in size, and it is not on a 4D sphere. But every measurement has a finite precision.

A similar situation already happened in the history of the physics. If you look around (i.e. make an experiment), you can see that the Earth is flat with zero curvature. But actually its curveture is not zero, but very small and your free eye experiment is not enough accurate. To find its exact curvature and to know that it is sphere, you need more accurate experimental data. In the case of the Universe, we don't have this. The few results we have show that the Universe is flat, or if it has a spherical geometry, its radius is at least 300 billion light years (reference).

The WMAP experiment and others are a stronger argument as the free eye experiment was for the flatness of the Earth: actually there were 3 independent, significantly different experiments with corresponding results:

  1. the WMAP
  2. 1a supernovas
  3. sorry I've forgot, if somebody knows and edits here, thank you very much

If the Universe is flat, it probably disproves that brane model you've read.

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