## Testing the Multiverse… Observationally!

[/caption]The multiverse theory is famous for its striking imagery. Just imagine our own Universe, drifting among a veritable sea of spontaneously inflating “bubble universes”, each a self-contained and causally separate pocket of higher-dimensional spacetime. It’s quite an arresting picture. However, the theory is also famous for being one of the most criticized in all of cosmology. Why? For one, the idea is remarkably difficult, if not downright impossible, to test experimentally. But now, a team of British and Canadian scientists believe they may have found a way.

Attempts to prove the multiverse theory have historically relied upon examination of the CMB radiation, relic light from the Big Bang that satellites like NASA’s Wilkinson Microwave Anisotropy Probe, or WMAP, have probed with incredible accuracy. The CMB has already allowed astronomers to map the network of large-scale structure in today’s Universe from tiny fluctuations detected by WMAP. In a similar manner, some cosmologists have hoped to comb the CMB for disk-shaped patterns that would serve as evidence of collisions with other bubble universes.

Now, physicists at University College London, Imperial College London and the Perimeter Institute for Theoretical Physics have designed a computer algorithm that actually examines the WMAP data for these telltale signatures. After determining what the WMAP results would look like both with and without cosmic collisions, the team uses the algorithm to determine which scenario fits best with the actual WMAP data. Once the results are in, the team’s algorithm performs a statistical analysis to ensure that any signatures that are detected are in fact due to collisions with other universes, and are unlikely to be due to chance. As an added bonus, the algorithm also puts an upper limit on the number of collision signatures astronomers are likely to find.

While their method may sound fairly straightforward, the researchers are quick to acknowledge the difficulty of the task at hand. As UCL researcher and co-author of the paper Dr. Hiranya Peiris put it, “It’s a very hard statistical and computational problem to search for all possible radii of the collision imprints at any possible place in the sky. But,” she adds, “that’s what pricked my curiosity.”

The results of this ground-breaking project are not yet conclusive enough to determine whether we live in a multiverse or not; however, the scientists remain optimistic about the rigor of their method. The team hopes to continue its research as the CMB is probed more deeply by the Planck satellite, which began its fifth all-sky survey on July 29. The research is published in *Physical Review Letters* and *Physical Review D*.

Source: UCL

### 24 Responses

### Leave a Reply

You must be logged in to post a comment.

I had always been led to believe that the human brain was much better at pattern recognition than any computer. Sounds like a project for Zooniverse.

Here are two relevant papers on the subject:

First Observational Tests of Eternal Inflation;

First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results (companion paper to the first one).

This is the kind of garbage that physicists do when they can’t advance the theory to the point that the multiverse is justified by a complete theory. What a bunch of crap.

U mad?

Theory is verified with observational evidence. If the evidence is not there, then it doesnt advance the theory. If the evidence is there, then it does. What part of this are you struggling to understand?

All I can see are your rantings of ignorance. What a bunch of crap.

Um, no, without a complete theory, this represents nothing more than designed speculation that the theory is being verified observationally. And they do it because they can’t advance the lame gravity theory.

Too cranky by far. You must be awful to be around, especially at home. Sounds like an alcohol problem.

I read into the first of these papers. It involves Weiner filter or transformation stuff. The data examined is numerical, and the picture we see is a visual representation. These analyses work with the actual power spectrum in numerical form.

LC

This sounds a bit like Gurzadyan & Penrose’s “concentric circles” in the WMAP data that supposedly might be evidence of pre-Big-Bang activity.

http://arxiv.org/abs/1011.3706

If I recall correctly this paper didn’t get a very positive reception.

You may remember this article that described their earlier work.

Their previous statistical analysis seems good enough:

“We assess which of the two models [the bubble collision hypothesis vs the standard hypothesis of fluctuations in a nearly Gaussian field] better explain the data by evaluating the Bayesian evidence for each.

The evidence correctly accounts for the fact that a more complex model (the bubble collisions, in this case) will generally fit the data better simply because it has more free parameters. This is the self-consistent statistical equivalent of applying Ockham’s Razor.”

In loose words, I believe they use the same approach that biologists use to find the (set of) most predictive trees. And as the biologists do when confronted with repetitious tasks, they seem to have implemented a mostly hands free computer software.

Nitpicks:

– There is no one multiverse theory, there are related theories. The latest fad of “bubble universe” theory comes out of “false vacuum” inflation as described by Nerlich here lately. Other theories comes out of “eternal” inflation et cetera.

– It is very easy to test multiverses in principle, and Bousso et al has predicted 6 main parameters successfully, which is more than the 5 that standard cosmology predicts. (Of course, standard cosmology also predicts many auxiliary observable parameters that multiverse theories are unable to do.)

The problem is if you accept environmental selection or not.

The Gurzadyan and Penrose critique is correct. You can click through my first link in my first comment to a good summary by Sean Carroll and a G&P response.

Essentially, as all greedy pattern searchers, G&P have found patterns but failed to test the null hypothesis sufficiently. Their patterns are predicted by the standard cosmology.

As you can see from the article and my previous comment, Peiris et al explicitly try to avoid that. “a statistical analysis to ensure that any signatures that are detected are in fact due to collisions with other universes, and are unlikely to be due to chance.”

The reluctance to accept environmental selection reminds me of early, purely philosophical, rows over different types of prediction.

It goes something like this:

1) Standard “black box” prediction of effective theories:

You see a wall enclosing an area, but can’t see over it. You predict that it is inhabited, because, well, that is what people can do. You throw a stone over the wall, because you expect inhabitants to clean the area.

After a while the stone is thrown back. Case closed.

2) Standard multiverse prediction:

You live in a room, but can’t open the doors. You predict that if there are other rooms, some sloppy inhabitants may have drilled through when trying to hang paintings.

After some scrutiny, you luck on some drill holes. Case closed.

3) Environmental selection prediction.

Same room, same doors. You predict that if there are other rooms, the room will be not too small or too wide (not typical house rooms).

The room is livable. Case closed.

This is not the same as the theory of Gurzadyan and Penrose. That involved an extension of the conformal past “to infinity,” where the big bang is a past Cauchy surface where the minimal information content of the universe is globally available. Some type of transition occurs with the occurrence of an event horizon. The cosmology tested here involves nucleation bubbles. It is analogous in some ways to ferromagnetism. Above the Curie temperature Iron atoms, which are little magnets, are oriented arbitrarily. If one applies a magnetic field to the hot iron these atoms orient accordingly. Once the temperature is lowered below the Curie point there is a scale at which this freedom of orientation of these atomic magnets is removed and they all sit in a domain with the same magnetic orientation. The cooler iron then has these many domains of magnetization. If one cools the iron below the Curie point while applying a magnetic field statistically these magnetic domains will be oriented along this magnetic field. This is BTW how the past history of the Earth’s magnetic field is inferred, where the basaltic material near the Atlantic spreading center holds this history of magnetic orientation in its magnetization. Something similar happens to the vacuum energy of the universe, where there are domains which break the symmetry of this high energy vacuum and the vacuum energy plummets to a much smaller value. These are then the “bubble universes,” of which in standard inflationary theory there are only so many of them. Eternal inflation posits an inflation which occurs at below the Planck scale, and so the inflaton field is not causally related to the expansion of the space and it acts “eternally.”

There are caveats I will have to make with this, before returning to the main issue here. Currently a Europhysics conference on data from the Large Hadron Collider has given a 2? exclusion for the Higgs particle this means the probability for the Higgs being absent is p = 1 – e^{-4?} = .98. In other words the darn things are pretty much excluded from the data. In the minimal supersymmetric standard model (MSSM) there are 8 degrees of freedom for the Higgs, where three of them at low energy are destroyed (Goldstone mechanism) and absorbed into the Z and W^{+/-} and the other five become a light neutral Higgs, a heavy neutral Higgs, a pseudoscalar and two charged Higgs fields. The game here ultimately involves putting enough degrees of freedom into the vacuum. Yet the predicted Higgs field are so far absent. The FERMI and INTEGRAL data on predicted dispersion of radiation across cosmic distances also illustrates how the vacuum is really free of all these vacuum modes our theories have been packing into them. This includes eternal inflationary cosmology. So all of this needs to be taken with caveats, and some sense that the foundations of physics involved here may simply be wrong.

The data analysis here involves detecting non-Gaussian structure in the CMB that may be a signature of some interaction between our inflationary cosmic bubble and some other. The pictures of the ovals with repeated wavy colored patterns in the paper http://arxiv.org/abs/1012.1995 are Legendre polynomial functions and the great summation over these results in the fine grained structure of the CMB we observe. Such an interaction would produce some breaking of the symmetry (anisotropy) in the distribution of the Gaussian signature.

LC

Do I read 2 breaking news stories here?

1. Higgs probably doesn’t exist, p=0.98

2. Eternal inflationary cosmology appears to be wrong. Does that also mean inflationary theory in general is in jeopardy? Since cosmological inflation seems to be eternal the way it is theorised if I’m well informed.

There is Higgs-like behavior. By this it means that quantum field theory goes haywire otherwise. The Higgs mechanism is really a form of phase transition similar to the onset of superconductivity. The standard Higgs model is a simple doublet of spinors, where 3 degrees of freedom, the goldstone boson are absorbed into the Z and W^{+/-} particle and the other at high enough energy is the Higgs condensate. The problem appears to be how we are assigning modes to the vacuum.

As for eternal inflation, that could be in trouble. When it comes to inflation, the old standard model of Guth, that is still good. Observational evidence for it is quite strong.

LC

I think you make some leaps here, to paint a pattern that you like:

“Eternal inflation posits an inflation which occurs at below the Planck scale,”

Haven’t we had this discussion before?

As I understand it the new slow-roll inflationary models do not occur at Planck scales.

The only requirement for eternal inflation is that the field is unbounded, so fluctuations restart inflation often enough. That takes the inflation field to below Planck scales.

The way to understand this is, I think, that the new observations putative indication of absence of structure at Planck scales means there is no spacetime magic connection to it. Likely the field model is an effective theory of inflation, which happens instead of spacetime. (I.e. it is obviously not the field of a real particle.)

So we could expect a similarly smooth behavior for inflation.

“Currently a Europhysics conference on data from the Large Hadron Collider has given a 2? exclusion for the Higgs particle this means the probability for the Higgs being absent is p = 1 – e^{-4?} = .98.”

A higgs is excluded at 2 sigma in many, but not all, regions. Combining all the data leaves a window between ~ 110 – 150 GeV, which is where it is expected:

“The sum total of the world’s data on precise measurements of the W and Z boson masses and properties, and the mass of the top quark, when taken together, tend to suggest a very light Higgs boson, much nearer 100 GeV. In fact the best predicted value for the Higgs boson mass is a good deal less than 80 GeV, but the LEP 2 experiments excluded a standard model Higgs boson with mass less than 114.4 GeV. This defines the low end of the present search window, which now extends to 150 GeV or so, and the precision data favor the low end of this range.”

And many detectors sees an excess in that region, which have set the experimentalists scurrying:

“But I think it’s safe to say that a lot of physicists are expecting the Higgs to show up, and the data presented so far does give them some hope. There is a small excess of events in the 130 to 150 GeV range in both detectors. “It should be noted that a modest excess of events is observed for Higgs boson masses below 145 GeV,” the CMS team has stated, noting that they should have a better handle on whether this excess is real within the next several months.”

“The FERMI and INTEGRAL data on predicted dispersion of radiation across cosmic distances also illustrates how the vacuum is really free of all these vacuum modes our theories have been packing into them. This includes eternal inflationary cosmology. ”

This predicts too much. Inflation is not a vacuum mode. Generic fluctuation eternal inflation isn’t either.

And I don’t see how “false vacuum” inflation of the kind discussed here is touched by those experiments. The inflation potential probed by the experiment is of the observable universe, not before reheating.

So predicting that this excludes inflation, if these experiments are accepted, hinges on the assumption that inflation is somehow a mundane particle field.

It could very well be correct: But to me it looks all too tenuous.

So in a few months, news headlines will be: “Global financial system collapses; Higgs particle discovered”

So in a few months, news headlines will be: “Global financial system collapses; Higgs particle discovered”

So in a few months, news headlines will be: “Global financial system collapses; Higgs particle discovered”

This is not the same as the theory of Gurzadyan and Penrose. That involved an extension of the conformal past “to infinity,” where the big bang is a past Cauchy surface where the minimal information content of the universe is globally available. Some type of transition occurs with the occurrence of an event horizon. The cosmology tested here involves nucleation bubbles. It is analogous in some ways to ferromagnetism. Above the Curie temperature Iron atoms, which are little magnets, are oriented arbitrarily. If one applies a magnetic field to the hot iron these atoms orient accordingly. Once the temperature is lowered below the Curie point there is a scale at which this freedom of orientation of these atomic magnets is removed and they all sit in a domain with the same magnetic orientation. The cooler iron then has these many domains of magnetization. If one cools the iron below the Curie point while applying a magnetic field statistically these magnetic domains will be oriented along this magnetic field. This is BTW how the past history of the Earth’s magnetic field is inferred, where the basaltic material near the Atlantic spreading center holds this history of magnetic orientation in its magnetization. Something similar happens to the vacuum energy of the universe, where there are domains which break the symmetry of this high energy vacuum and the vacuum energy plummets to a much smaller value. These are then the “bubble universes,” of which in standard inflationary theory there are only so many of them. Eternal inflation posits an inflation which occurs at below the Planck scale, and so the inflaton field is not causally related to the expansion of the space and it acts “eternally.”

There are caveats I will have to make with this, before returning to the main issue here. Currently a Europhysics conference on data from the Large Hadron Collider has given a 2? exclusion for the Higgs particle this means the probability for the Higgs being absent is p = 1 – e^{-4?} = .98. In other words the darn things are pretty much excluded from the data. In the minimal supersymmetric standard model (MSSM) there are 8 degrees of freedom for the Higgs, where three of them at low energy are destroyed (Goldstone mechanism) and absorbed into the Z and W^{+/-} and the other five become a light neutral Higgs, a heavy neutral Higgs, a pseudoscalar and two charged Higgs fields. The game here ultimately involves putting enough degrees of freedom into the vacuum. Yet the predicted Higgs field are so far absent. The FERMI and INTEGRAL data on predicted dispersion of radiation across cosmic distances also illustrates how the vacuum is really free of all these vacuum modes our theories have been packing into them. This includes eternal inflationary cosmology. So all of this needs to be taken with caveats, and some sense that the foundations of physics involved here may simply be wrong.

The data analysis here involves detecting non-Gaussian structure in the CMB that may be a signature of some interaction between our inflationary cosmic bubble and some other. The pictures of the ovals with repeated wavy colored patterns in the paper http://arxiv.org/abs/1012.1995 are Legendre polynomial functions and the great summation over these results in the fine grained structure of the CMB we observe. Such an interaction would produce some breaking of the symmetry (anisotropy) in the distribution of the Gaussian signature.

LC

the assumption is that there are a lot of adjacent ‘bubbles.’

the next one may be far away indeed.

so, how to map the impingement profile?

map the z (redshift)!

is this a poem about the foam?

If the extrauniversal bubbles are not adjacent to our universe, their existence cannot be demonstrated in this way. Nor in any other way probably. Science is limited to what is observable..

You may want to read the post above.

I suppose you mean the article by Bousso et al? You just showed me a whole new world: The entropic principle etc., I tried to read it but it’s so hard… Do you think by this method any detailed information about non-adjacent universes can be obtained? Doesn’t a change in entropy only tell us how much complexity is changed simultaneously, not how it is changed? In other words, by this method could we determine that something must be going on outside our universe, but we still can’t say what that would be, only how much is going on?