Has this idea been explored? Dark matter as matter in parallel universes...

twofish-quant

I strongly suspect that this isn't the case, and if you get a multiple universe theory to the point where you can fit the data, then it will be as complex if not more complex than what we have now. If you have a complex theory, then adding universes to the theory makes things more complex and not less complex.

I'd be interested in hearing why you would think otherwise.

Misericorde

How can a multiple universe theory of dark matter POSSIBLY be LESS complex? You'll need to include all of the elements of the a one-universe cosmology, and in addition you have to figure out how two spatially and temporally separated bubbles interact in what seems like a pretty uniform manner. Seems a bit mad to me as a matter of fact, and again, against the spirit of a multiverse if not every possible practice of one.

DavidMcC

This, for example:
http://www.scribd.com/doc/4787671/Th...nd-Dark-Energy
"... This alleviates the classical problem of the curious energy scale of order a millielectronvolt associated with a constant lambda."

Chalnoth

The cosmological constant is constant in both time and space. Perhaps you were thinking of the misnamed Hubble constant?

Chalnoth

There are indeed many speculative alternatives to the cosmological constant that vary in time. But there is as yet no evidence of time-variation of dark energy. And the "fine tuning" argument here is a non-argument because the anthropic selection effect guarantees that the cosmological constant be small anyway.

DavidMcC

"Smolin-esque" LQG-based BH cosmology only requires a few reasonable additions to at least provide a framework for making sense of what is otherwise just bizarre. (The main one is that "space-loops" are only linked within a space that is generated from the collapse of a single body, and that may already have been in Smolin's own version.) I've listed the rest several times before on this and other sites. The pro-matter, ant-anti-matter bias of the universe is one, as it suggests that what banged was somehow contaminated, as if having been condensed previously from part of a previous, much bigger universe. The apparent "fine-tuning" of the laws to the possibility of abiogenesis is another - this is the only way we might find ourselves in a universe in which the fundamental constants were just so, otherwise it would have to have been extraordinary lucky.
Etc.

stefanbanev

You probably just ignore the evidences, in fact there are plenty experimental data supporting non-constant agenda. Specifically, the varying "alpha" has been reported for 15+ years, the recent report (see below) for the spacial alpha anisotropy explains the inconsistencies of previous reports.

Refs:
arxiv.org/abs/1008.3907: Evidence For Spatial Variation Of The fiFine
Structure Constant
arxiv.org/abs/1008.3957: Manifestations Of A Spatial Variation Of
Fundamental Constants On Atomic Clocks, Oklo,
The popular overview:
http://www.sciencedaily.com/releases...0909004112.htm

BTW, the dark matter flow correlates with alpha gradient (see http://en.wikipedia.org/wiki/Dark_flow)

Stefan

Misericorde

I was under the impression that 'Dark Flow' is at the level of, "might be something, might be an irregularity on the image."? It seems everyone uses this one to justify some claim, from colliding universes and more. In terms of established science, you seem to be going on with a bit of nonsense there stefanbanev, or at least grossly overreaching.

@DavidMcC: Or, while I don't believe this, the 'eternal inflationists' could be right and we're part of an infinite set of universes, no more or less unique than any other part of an infinite grouping. When there is NOTHING to point one way or another, what is the point in all of this?

Chalnoth

Um, that's a completely separate issue from the cosmological constant. [itex]\alpha[/itex] and [itex]\Lambda[/itex] are completely different parameters.

But it's largely shown to be bunk.

The basic idea behind the varying alpha is that if the fine structure constant were to vary, then atoms would not just have redshifted or blueshifted spectra, but the entire pattern of spectral lines changes, especially for heavier atoms. So the experimental team looked for these changes in the patterns of the more massive elements, such as Carbon and Oxygen, in distant quasars. The difficulty here is that the signatures of these elements are really, really faint, so they can only barely see them against the background. And the spectral signatures of these elements are also quite complex, with lots and lots of spectral lines, so that it's not at all clear which line belongs to which atom.

So, in the end, it turns out that they're just fitting the background noise. This is supported by the fact that there is no consistency between the measurements of [itex]\alpha[/itex] between different quasars, and different experimental teams trying to replicate their results have come up with completely different results.

George Jones

Cosmo Novice, perhaps you were thinking of

http://www.physicsforums.com/showthr...35#post3330035.

Or did you really mean the cosmological constant?

stefanbanev

Chalnoth> But it's largely shown to be bunk.

Please be more specific; is it shown by whom (reference please)?

Chalnoth> So, in the end, it turns out that they're
Chalnoth> just fitting the background noise.

No offence, but may you buck it by something more tangible then just your opinion?

Regards,
Stefan

Chalnoth

It's backed up by their very own work:
http://arxiv.org/abs/1008.3907

Inconsistent results are a hallmark of badly-done science.

Cosmo Novice

Thankyou Chalnoth and George, I was a little confused and thinking of the hubble constant!

stefanbanev

Thanks for reference, it's not 100% definitive but clearly supports your position.

Stefan

Misericorde

It's not 100%, but it's pretty fat nail in that coffin. A lot of the "Dark" stuff other than matter is used to justify any number of pet theories; tread with care.

stefanbanev

It's very true. I'm bias for any experimental evidence for "multiverse" support because it's its weakest spot. I still think that the traditional scientific method should work for such "metaphysics" frontier even it may be flexed quite a bit. The proposed "statistical" methods are indirect and prone to interpretations; therefore, those direct observation for alpha appeals a lot...

Chalnoth

I was pretty excited about it the first time I heard about it too. I've just become a bit jaded after learning more about it.