New cosmology - dark energy unnecessary

[hellfire]

I don't like superhorizon modes because they are not meaningful in our Hubble bubble.

I think it is not consistent to argue that superhorizon modes cannot exist, if one accepts the standard cosmological model. Superhorizon modes are a natural consequence of inflation and the current model for formation of large scale structure relies on this: Classical perturbations are produced from quantum fluctuations in a de Sitter background by modes with wavelengths larger than horizon size during inflation, which were frozen at a nonzero value and re-entered the horizon after subsequent expansion of space. If superhorizon modes existed then, why shouldn’t they exist now? It seams to me that it would be a coincidence if the production of superhorizon modes had lead to modes which are exactly less of equal to the current Hubble length.

And theoretically they appear to be invalid according to more recent sources [see links].

May be I overlooked this, but I did not find arguments against superhorizon modes in the referenced papers. Could you specify, please?

 

[Chronos]

That was an admittedly poor choice of words. The existence of superhorizon modes is not an issue, just the effects.

 

[Kea]

corrected version

Version 4 is now available:

Viable exact model universe without dark energy from primordial inflation
David L. Wiltshire
http://www.arxiv.org/abs/gr-qc/0503099

 

[marcus]

Version 4 is now available:

Viable exact model universe without dark energy from primordial inflation
David L. Wiltshire
http://www.arxiv.org/abs/gr-qc/0503099

In the acknowledgments section of version 3 he only thanked one colleague (Roy Kerr) but now he must have received many helpful comments because in version 4 he thanks many more people. Ten, if I counted correctly, including some who are well known to us.

 

[ohwilleke]

Wiltshire's paper is basically doing what tired light, intrinsic redshift and other redshift relation doubters have been looking for, but have failed to do in a convincing way. It hypothesizes that there is a flaw in the standard redshift-distance relation, and that this flaw makes much of the unexplained weirdness in cosmology (in Wiltshire's case dark energy, cosmic accelleration, WMAP implication of early structure formation, and large scale curvature of any meaningful amount) vanish in one fell swoop.

Wiltshire also has the virtue of, at least Wiltshire claims, doing what Kolb did the hard way with an exact solution, rather than a lot of physicist approximations and hand waving.

Wiltshire's justification for the standard redshift-distance relation flaw basically flows from an assumption that the super-horizon universe has a particular density, and that our existing models do a poor job of matching the data to a time scale that makes sense for that data as a result.

One wants to root for Wiltshire. A non-weird cosmology is very attractive. Throw in a 4D LQG, which gets rid of the multi-dimensional weirdness and the abundant undiscovered particle predictions of M-theory, eliminates the singularities of GR, and which also has a non-abelian gravity which in turn could imply something like MOND (and hence eliminate the need for dark matter), and you get to a place where you can describe the observed phenomena of the universe with a formalism that doesn't make your head explode or imply a lot of new phenomena that we've never seen. Everything starts to make sense in a fairly straightforward way.

Of course, this makes most of what the mainstream science press and a super-majority of the cosmology and string theory (i.e. theoretical quantum physics) community has said for the past couple of decades sound like wacky hallucinating conjecture, but hey, lifes a b--- and then you die.

On the other hand, the standard redshift-distance relation has held up very robustly thus far in the face of numerous flawed attempts to explain away the weirdness that this model implies when you look at the data, and it is difficult to believe that this relation can really be disturbed by something as modest as some modest assumptions about the density of matter-energy in a super-horizon region. Isn't the relation more robust than that? Hence, serious skepticism is in order. I can't follow the math in Wiltshire rigorously enough to see if there is a conceptual flaw in his argument for a conversion between a "measured Hubble constant" and a "true Hubble constant". But, there are plenty of people who are capable of doing so, and since the Kolb paper has attacted so much attention, and Wiltshire himself appears to have received so many comments in a fairly short time period, one would hope that this could be sorted out fairly quickly.

 

[Chronos]

v4 is a definite improvement in my mind [which is not necessarily a good sign]. Some of my issues with the initial release have been placated. I still have difficulty grasping the consequence of super horizon fluctuations within our Hubble bubble. I am stuck on the notion this is like trying to view IR wavelengths through a UV filter. I wonder though, is the intent to suggest that accelerated expansion is an illusion created by interference fringes in the super horizon fluctuations? The assertion our observable bubble was causally connected to the bulk universe prior to inflation is also troubling. I can't shake the feeling there is something paradoxical about being causally connected to unobservable regions of the universe. I will, however, allow that I may be a little too narrow minded of what constitutes being observable.

 

[ohwilleke]

Chronos, I see the intuition your getting at and in the same vein wonder if the effect Wiltshire proposes doesn't imply superluminal gravitational action.

 

[Kea]

Just Out

Exact model universe fits type IA supernovae data with no
cosmic acceleration
B.M.N. Carter, B.M. Leith, S.C.C. Ng, A.B. Nielsen, D.L. Wiltshire
http://www.arxiv.org/abs/astro-ph/0504192

9 pages, 5 figures, aastex

Abstract:
The unexpected dimness of Type Ia supernovae at redshifts z <~1 has over the past 7 years been seen as an indication that the expansion of the universe is accelerating. A new model cosmology has been proposed by one of us [gr-qc/0503099], based on the idea that our observed universe resides in an underdense bubble remnant from a primordial epoch of cosmic inflation. Although there is no cosmic acceleration, it is claimed that the luminosity distance of type Ia supernovae data will nonetheless fit the new model, due to systematic effects. In this paper the hypothesis is tested statistically against the available type Ia supernovae data by both chi-square and Bayesian methods. The model gives good agreement if the density parameter, Omega_0, is taken to be the density in ordinary baryonic matter only. If low Omega_0 parameter values are accepted, then the model would dispense with both dark energy and non-baryonic dark matter, and an alternative explanation would be required for galaxy rotation curves and dynamical measurements of Omega_0 on the scales of clusters of galaxies.

 

[ohwilleke]

If low Omega_0 parameter values are accepted, then the model would dispense with both dark energy and non-baryonic dark matter, and an alternative explanation would be required for galaxy rotation curves and dynamical measurements of Omega_0 on the scales of clusters of galaxies.

:!) It will be very interested to see what informed reviews have to say about this theory. or or or

But, enough with the decedant smilies already.

 

[Kea]

The following webpage is under construction:

Open Bubble Model Cosmology by D.L. Wiltshire

http://www2.phys.canterbury.ac.nz/~dlw24/universe/

 

[Kea]

New

New versions now available:

http://www2.phys.canterbury.ac.nz/~dlw24/universe/

Greetings
Kea

 

[Kea]

new paper

Structured FRW universe leads to acceleration: a non-perturbative approach
Reza Mansouri
http://www.arxiv.org/abs/astro-ph/0512605

From abstract:
We propose a model universe in the matter dominated phase described by a FRW background with local inhomogeneities, like our local patch, grown out of the primordial fluctuations. Our local patch consisting of different structures is approximated as an inhomogeneous cosmic fluid described by a LTB metric embedded in a background FRW universe. Within the exact general relativistic formulation, the junction conditions for the only possible matching without a thin shell at the boundary, neglected so far in the literature, constrains the model in such a way that the luminosity distance-red shift relation mimics a FRW universe with dark energy. Therefore, the dimming of SNIa is naturally accounted for in such a structured FRW universe.

 

[Chronos]

I read that paper and agree it's an interesting idea, Kea. It appears not to require those annoying, ad hoc parameters.