# Does our universe rotate ?

1. May 19, 2005

### wolram

http://arxiv.org/PS_cache/astro-ph/pdf/9703/9703082.pdf

http://arxiv.org/abs/gr-qc/9604049

Authors: V.A. Korotky, Yu.N. Obukhov
Journal-ref: Published in Gravity, Particles and Space-Time'', eds. P. Pronin and G. Sardanashvily (World Scientific: Singapore, 1996), pp. 421-439

We overview our recent studies of cosmological models with expansion and global rotation. Problems of the early rotating models are discussed, and the class of new viable cosmologies is described in detail. Particular attention is paid to the observational effects of the cosmic rotation.

Global rotation would i guess make a huge difference to cosmology, but it
seems it is not a great topic in the literature, i can only wonder how the
angular mommentum component would change astro phys, ie rotation
non rotation.

Last edited: May 19, 2005
2. May 19, 2005

### wolram

http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:astro-ph/0409073

Authors: Godlowski, Wlodzimierz; Szydlowski, Marek

We analyze dynamics of the FRW models with global rotation in terms of dynamical system methods. We reduce dynamics of these models to the FRW models with some fictitious fluid which scales like radiation matter. This fluid mimics dynamically effects of global rotation. The significance of the global rotation of the Universe for the resolution of the acceleration and horizon problems in cosmology is investigated. It is found that dynamics of the Universe can be reduced to the two-dimensional Hamiltonian dynamical system. Then the construction of the Hamiltonian allows for full classification of evolution paths. On the phase portraits we find the domains of cosmic acceleration for the globally rotating universe as well as the trajectories for which the horizon problem is solved. We show that the FRW models with global rotation are structurally stable. This proves that the universe acceleration is due to the global rotation. It is also shown how global rotation gives a natural explanation of the empirical relation between angular momentum for clusters and superclusters of galaxies. The relation $J \sim M^2$ is obtained as a consequence of self similarity invariance of the dynamics of the FRW model with global rotation. In derivation of this relation we use the Lie group of symmetry analysis of differential equation.

3. May 19, 2005

### wolram

I find quite amazing, a two hour search of the net came up with next to nothing
on this subject, i think it is one of the most basic properties of our universe, if
we have no knowledge of the motion of our U, "rotating or not", how can we
explain with any certainty the dynamics within it?
I don't know if the subject is to problematic to solve, or it is just overlooked
in the literature, "may be i am looking in the wrong places", but the two papers
i have posted contain the bulk of information.

4. May 19, 2005

### wolram

I guess one can ask, "rotating relative to what", but to me that is a circular
question, better rephrased as "does the universe have angular momentum"?

5. May 19, 2005

### wolram

The best information i can find suggests that our universe is rotating,
but the problems that arise from this rotation are ignored by cosmologists.
One of these problems is, it would falsify the Big bang, i do not know how
or why.
another is it would infer a preferred direction, i guess this is true, but it
would depend on the speed of this rotation for any observational effects
to be apparent.

6. May 19, 2005

### Mike2

If the universe started from a singularity, and was in thermal equilibrium, then there is no way it could acquire a global rotation.

If there were a preferred direction then galaxies moving in the direction for rotation would have a higher component of centrifigal force accelerating it away more than those galaxies traveling in the opposite direction to this rotation. Since we do not see a recessional velocity of galaxies depending on their direction of travel, then we should conclude that it does not exist. Besides, a center point or axis of the universe would have to be identified in order to have a global rotation presumably around it, right? This would violate any spherical symmetry the universe might have had.

7. May 19, 2005

### wolram

----------------------------------------------------------------------
The universe is a big place, rotation could be non trivial, but difficult to
detect, depending on the observers possition.

8. May 19, 2005

### Chronos

Rotating relative to what is a valid question. Superhorizon modes is one possibility. The existence, or ability of causally disconnected regions of the universe to affect the observable universe has been rather hotly debated. The nays appear to have the upper hand for the time being.

In hydrodynamic models, rotation does lead to observable consequences. If the universe behaves according to such a model [which is in itself an issue] this could should show up as anomalous motion in large scale structures, like galactic clusters. It is, however, more likely and easily detected in the CMB - especially the polarization map. The year 2 WMAP results may shed some light on this [and could be the reason its release has been delayed].

The more troubling aspect of this rotation business is it would run contrary to one of the more cherished assumptions of GR - that the universe looks the same regardless of location. A rotating universe would necessarily have an axis of rotation effectively confering it a center - which could be construed as a preferred reference frame.

All said, a rotating universe would create at least as many headaches as it might solve, hence cosmologists cannot be expected to rush to embrace it. Like most of the rest of us, they have a fondness for ideas that make life simpler.

9. May 19, 2005

### Mike2

And it would also contradict the FRW metric which assumes homogeneity and isotropy from a singularit.

10. May 20, 2005

### wolram

Chronos
All said, a rotating universe would create at least as many headaches as it might solve, hence cosmologists cannot be expected to rush to embrace it. Like most of the rest of us, they have a fondness for ideas that make life simpler

I agree on keeping things simple Chronos,i thought resurrecting this rotating U was a good idea
for debate,as understanding any dynamics our U has is basic to understanding anything that
happens within it, I doubt if finding some rotation would be as problematic as discovering
the the U is not static but expanding.
Mike2
Is a center so bad? I agree that something that is an infinite infinite can not have a center,
but this thing we call a bounded infinity has the properties that are so unintuitive.

11. May 20, 2005

### wolram

Last edited: May 20, 2005
12. May 20, 2005

### wolram

13. May 20, 2005

### wolram

http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:astro-ph/0008089

This thesis concerns the compatibility of inhomogeneous cosmologies with our present understanding of the universe. It is a problem of some interest to find the class of all relativistic cosmological models which are capable of providing a reasonable fit' to the universe. This thesis, in some respects, is part of this process. We consider Stephani models, which are a generalisation of the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) models, which can be thought of as FLRW models with acceleration and pressure gradients. Thus these models generalise the dust' assumption of standard cosmology. The crucial aspect of this work is the retention of the Copernican principle -- an assumption regarded by many as crucial to cosmology. It states that we are not at a special location in the universe. This is a vital aspect of the original work in this thesis: consideration of an inhomogeneous model, while retaining the Copernican principle has, as far as the author is aware, not been considered in detail before. We start by generalising the Ehlers-Geren-Sachs Theorem to identify the class of inhomogeneous spacetimes which allow an isotropic radiation field for all observers in the spacetime. We then investigate observational and physical aspects of these models from all observer locations. We conclude that there exist spacetimes which conform to present observational constraints (especially anisotropy constraints) for any location in the spacetime, while at the same time being significantly inhomogeneous; ie, not `almost-FLRW'.

This Thesis is 118 pages and covers a lot of ground, i have not read it all yet.

14. May 21, 2005

### wolram

Last edited: May 21, 2005
15. May 21, 2005

### wolram

http://arxiv.org/abs/astro-ph/0008106

Authors: Yuri N. Obukhov
Comments: Revtex, 85 pages, no figures; ref. list is updated as compared to the published version
Journal-ref: Published in "Colloquium on Cosmic Rotation", Eds M. Scherfner, T. Chrobok and M. Shefaat (Wissenschaft und Technik Verlag: Berlin, 2000) pp. 23-96

An overview of the cosmological models with expansion, shear and rotation is presented. Problems of the rotating models are discussed, their general kinematic properties and dynamical realizations are described. A particular attention is paid to the discussion of possible observational effects which could be used to estimate or to put limits on the cosmic rotation.

16. May 21, 2005

### Garth

It seems to me that if the universe could rotate then it should. Otherwise, for rotation as a whole to be possible and yet the universe 'select' to have zero rotation would appear contrived.

If the universe is rotating then that rotation should be observable as an anisotropy, either of the galactic field or the CMB or probably both.

Such rotation does not appear to have been observed, therefore one conclusion is that not only is the universe not rotating but that it cannot rotate. This would seem to be consistent with Mach's Principle, i.e. there is nothing for the universe to rotate with respect to.

Garth

Last edited: May 21, 2005
17. May 21, 2005

### wolram

Garth, did you read page 6 of last post? or any?

18. May 21, 2005

### Garth

I did and I was agreeing with you!

Garth

19. May 21, 2005

### wolram

Garth my apiologies, i was being over protective and vein, it seems that my
outlook is as an outsider, so i tend to overreact, i do wish that other or not
well understood theories were taken into account, it may make a huge difference to our understanding, but the many rule, and it is difficult to see
where they are are going

20. May 25, 2005

### sonhouse

Hi all, just a thought about the rotation idea:
It occured to me reading the statement that if the universe was rotating, we would see differential motions in certain directions which we don't therefore there is no rotation. The thing I was thinking is this: first, if the universe were rotating, would it be flattened like jupiter or the sun, "equitorial" bulge and all, second, if the dark matter is so prevalent in the universe, could not a situation occur here like what we see in the rotation of galaxies where they act as if they were all sitting on a lazy susan, that is to say all the galaxy rotates at the same rate presumably because of this massive hidden mass keeping the whole thing in lock-step rotation wise. If something like that were going on in the universe as a whole, wouldn't any differential rotation data be lost, just like the rotation rates vs. the radius of galaxies?