Dark matter as matter in parallel universes

[DavidMcC]

What are you going on about? There is no evidence as of yet that the cosmological constant isn't constant, and dark matter is expected to be extremely hard to detect, so it's hardly a surprise we haven't yet.

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

 

[Chalnoth]

I was under the impression the cosmoloigcal contant is theoretically constant. It is not temporally constant (ie: it changes over time) but is spatially constant.

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

 

[Chalnoth]

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

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]

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.

"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]

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.

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 spatial 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/2010/09/100909004112.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]

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 spatial 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/2010/09/100909004112.htm

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

Stefan

Um, that's a completely separate issue from the cosmological constant. $\alpha$ and $\Lambda$ 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 $\alpha$ between different quasars, and different experimental teams trying to replicate their results have come up with completely different results.

 

[George Jones]

I was under the impression the cosmoloigcal contant is theoretically constant. It is not temporally constant (ie: it changes over time) but is spatially constant.

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

Cosmo Novice, perhaps you were thinking of

https://www.physicsforums.com/showthread.php?p=3330035#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]

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

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

We previously reported observations of quasar spectra from the Keck telescope suggesting a smaller value of the fine structure constant, alpha, at high redshift. A new sample of 153 measurements from the ESO Very Large Telescope (VLT), probing a different direction in the universe, also depends on redshift, but in the opposite sense, that is, alpha appears on average to be larger in the past.

Inconsistent results are a hallmark of badly-done science.

 

[Cosmo Novice]

Cosmo Novice, perhaps you were thinking of

https://www.physicsforums.com/showthread.php?p=3330035#post3330035.

Or did you really mean the cosmological constant?

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

 

[stefanbanev]

Inconsistent results are a hallmark of badly-done science.

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

Stefan

 

[Misericorde]

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

Stefan

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 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.

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]

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...

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.

 

[Misericorde]

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.

I'd agree with that; it's hard not to become enamored with these ideas, but it's also hard not to fall out of love with them given time and reading. It's one of the joys of science that you get these amazing concepts to bat around, but the other side is the need for rigor. Without any hope of falsification or validation, someday yah just got to move on I guess. I don't feel that physics has given us a handle on the nature of existence, just what it's meant to do: help us understand how the slice of reality we deal with operates, by what rules, and what constants exist. The how and why of it all seems to be an eternal question that is always, "just around the corner," and never is.

 

[DavidMcC]

@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?

I am not an "eternal inflationist" either, but I 've posted a lot in various threads about "what the point of all this is". In a nutshell, laws of physics that don't seem quite right - that look as if they're the product of interaction within a multiverse that can only be detected through gravity, but not light (expalining also why a lot of people discount the idea - you know, the "if you can't see it with light, it isn't there" attitude).

 

[Misericorde]

I am not an "eternal inflationist" either, but I 've posted a lot in various threads about "what the point of all this is". In a nutshell, laws of physics that don't seem quite right - that look as if they're the product of interaction within a multiverse that can only be detected through gravity, but not light (expalining also why a lot of people discount the idea - you know, the "if you can't see it with light, it isn't there" attitude).

The laws of physics seem just fine, but our understanding of them leaves something to be desired. Why is that surprising, and why do you think the solution is anything other than the natural evolution of existing theories and development of new ones? Where does metaphysics enter the picture except to make people feel comfy or entertained while the real work of progress in the understanding of nature moves forward?

 

[DavidMcC]

The laws of physics seem just fine, but our understanding of them leaves something to be desired. Why is that surprising, and why do you think the solution is anything other than the natural evolution of existing theories and development of new ones? Where does metaphysics enter the picture except to make people feel comfy or entertained while the real work of progress in the understanding of nature moves forward?

They may seem "fine" to you, misericode, but I have noticed that some of them lack the simplicity and symmetry that one might expect of a universe made in the conventional way. Eg, there shouldn't have been an excess of matter over anti-matter, etc (as I've listed before). One example of "fine" is E=Mc^2, but most other physics looks dodgy, and that includes GR+ (ie, GR with the CC). Various aspects of cosmology, including dark matter, inflation, the existence of life, etc (I've listed them before), suggest that, even though we don't see other big bangs with light, they must have occurred in any case, and set up a situation in which we observe their interactions with each other, then struggle to fit them into a theory that denies their existence. Thus, I think understanding nature will only move forward when we stop denying that a big bang, as a natural process, must have happened randomly many times, and not in a neat serial row.
EDIT: In other words, I think it is absurd to dismiss the Smolin's LQG as meer metaphysics. Rather it is the "head in the sand" attitude to the multiple challenges to "one universe" that is the problem, generating all kinds of bizarre "explanations".

 

[Misericorde]

They may seem "fine" to you, misericode, but I have noticed that some of them lack the simplicity and symmetry that one might expect of a universe made in the conventional way. Eg, there shouldn't have been an excess of matter over anti-matter, etc (as I've listed before). One example of "fine" is E=Mc^2, but most other physics looks dodgy, and that includes GR+ (ie, GR with the CC). Various aspects of cosmology, including dark matter, inflation, the existence of life, etc (I've listed them before), suggest that, even though we don't see other big bangs with light, they must have occurred in any case, and set up a situation in which we observe their interactions with each other, then struggle to fit them into a theory that denies their existence. Thus, I think understanding nature will only move forward when we stop denying that a big bang, as a natural process, must have happened randomly many times, and not in a neat serial row.
EDIT: In other words, I think it is absurd to dismiss the Smolin's LQG as meer metaphysics. Rather it is the "head in the sand" attitude to the multiple challenges to "one universe" that is the problem, generating all kinds of bizarre "explanations".

Uh huh, yet they predict and let us develop technology for all that it lacks the elegance you seem to want.

 

[DavidMcC]

Uh huh, yet they predict and let us develop technology for all that it lacks the elegance you seem to want.

LQC also makes predictions (and could have done so before if it hadn't been prematurely abandoned). Eg, it predicts that neither WIMPS nor MACHOS, etc will be found, and that dark energy will ultimately go to zero (when there is nothing more to feed on in the parent universe), although the time-scale for this is unclear.
It is not that I "want elegance", it's just that I see inelegance elsewhere in physics, in which it is caused by external effects. Eg, if you didn't know that the Earth was slowly rotating, you would just have to accept that Newton's law of motion, F=ma, was a mess, needing to have some strange extra terms (the Coriolis force, etc) to make it correct.
As foir technology, comparing any theories should produce that, it's nothing to do with which is better.

 

[Chalnoth]

LQC also makes predictions (and could have done so before if it hadn't been prematurely abandoned). Eg, it predicts that neither WIMPS nor MACHOS, etc will be found, and that dark energy will ultimately go to zero (when there is nothing more to feed on in the parent universe), although the time-scale for this is unclear.

Er, what? Where does it make these predictions? And if so, how the hell does it explain our observations of dark matter?

 

[Misericorde]

Er, what? Where does it make these predictions? And if so, how the hell does it explain our observations of dark matter?

Ditto.

 

[David Elm]

The parallel universe part of your idea doesn't seem to hold water. If gravity was acting in more than 3 dimensions, then it would spread out faster than it currently does (1/r^2). I think this has been well measured and precluded.

On the other hand, I've seen some papers in the ArXive (xxx.lanl.gov) that indication that idea of self-interacting dark matter has some merit.

There is also a non-mainstream theory (developed by serious physicists, not fringe guys, but still not generally accepted) called "mirror matter" that proposes that there are two mutually invisible types of matter living in the same space. I don't know if I follow the argument that well, but it has to do with having two types of matter that violate CP conservation in opposite ways.

Other than the "mirror matter" development, I haven't seen much in the way of a theory of what that self interacting dark matter might be. One paper proposed an analogy to electrodynamics within dark matter, but they didn't go so far as to propose a different type of equivalent matter that was somehow different.

Perhaps these researchers are being deliberately cautious until they come across a good enough theory to hang their collective hats on.