Bumping bubbles from our pre-bang past ( test of eternal infl.)

[marcus]

Bumping bubbles from our pre-bang past ("test" of eternal infl.)

http://arxiv.org/abs/1012.1995
First Observational Tests of Eternal Inflation
Stephen M. Feeney (UCL), Matthew C. Johnson (Perimeter Institute), Daniel J. Mortlock (Imperial College London), Hiranya V. Peiris (UCL)
5 pages, 2 figures, companion paper forthcoming
(Submitted on 9 Dec 2010)
"The eternal inflation scenario predicts that our observable universe resides inside a single bubble embedded in a vast multiverse, the majority of which is still undergoing super-accelerated expansion. Many of the theories giving rise to eternal inflation predict that we have causal access to collisions with other bubble universes, opening up the possibility that observational cosmology can probe the dynamics of eternal inflation. We present the first observational search for the effects of bubble collisions, using cosmic microwave background data from the WMAP satellite. Using a modular algorithm that is designed to avoid a posteriori selection effects, we find four features on the CMB sky that are consistent with being bubble collisions. If this evidence is corroborated by upcoming data from the Planck satellite, we will be able to gain insight into the possible existence of the multiverse."

This appeared at arxiv.org preprint site on Friday 10 December.
At this point it seems like just a speculative notion. They need further data if they want to make a more of a real case.
The MIT Tech Review reminded readers of the "face" on Mars that at one time people saw sculpted in Martian terrain.

Thanks to MTd2 for spotting this item and tipping us to it.

 

[marcus]

The MIT Tech Review had this journalistic account (also mentioning Penrose Conformal Cyclic cosmology and the concentric circle evidence for it that was recently offered.)

==quote Tech Review==
Astronomers Find First Evidence Of Other Universes
Our cosmos was "bruised" in collisions with other universes. Now astronomers have found the first evidence of these impacts in the cosmic microwave background

There's something exciting afoot in world of cosmology. Last month, Roger Penrose at the University of Oxford and Vahe Gurzadyan at Yerevan State University in Armenia announced that they had found patterns of concentric circles in the cosmic microwave background, the echo of the Big Bang.

This, they say, is exactly what you'd expect if the universe were eternally cyclical. By that, they mean that each cycle ends with a big bang that starts the next cycle. In this model, the universe is a kind of cosmic Russian Doll, with all previous universes contained within the current one.

That's an extraordinary discovery: evidence of something that occurred before the (conventional) Big Bang.

Today, another group says they've found something else in the echo of the Big Bang. These guys start with a different model of the universe called eternal inflation. In this way of thinking, the universe we see is merely a bubble in a much larger cosmos. This cosmos is filled with other bubbles, all of which are other universes where the laws of physics may be dramatically different to ours.

These bubbles probably had a violent past, jostling together and leaving "cosmic bruises" where they touched. If so, these bruises ought to be visible today in the cosmic microwave background.

Now Stephen Feeney at University College London and a few pals say they've found tentative evidence of this bruising in the form of circular patterns in cosmic microwave background. In fact, they've found four bruises, implying that our universe must have smashed into other bubbles at least four times in the past.

Again, this is an extraordinary result: the first evidence of universes beyond our own.

So, what to make of these discoveries. First, these effects could easily be a trick of the eye. As Feeney and co acknowledge: "it is rather easy to find all sorts of statistically unlikely properties in a large dataset like the CMB." That's for sure!

There are precautions statisticians can take to guard against this, which both Feeney and Penrose bring to bear in various ways.

But these are unlikely to settle the argument. In the last few weeks, several groups have confirmed Penrose's finding while others have found no evidence for it. Expect a similar pattern for Feeney's result.

The only way to settle this will be to confirm or refute the findings with better data. As luck would have it, new data is forthcoming thanks to the Planck spacecraft that is currently peering into the cosmic microwave background with more resolution and greater sensitivity than ever.

Cosmologists should have a decent data set to play with in a couple of years or so. When they get it, these circles should either spring into clear view or disappear into noise (rather like the mysterious Mars face that appeared in pictures of the red planet taken by Viking 1 and then disappeared in the higher resolution shots from the Mars Global Surveyor).

Planck should settle the matter; or, with any luck, introduce an even better mystery. In the meantime, there's going to be some fascinating discussion about this data and what it implies about the nature of the Universe. We'll be watching.
==endquote==
http://www.technologyreview.com/blog/arxiv/26132/

 

[Rick88]

Truly fascinating.

 

[M. Bachmeier]

If such ideas hold will our (universe as we know it) get downgraded to a sub-universe. First Pluto then the universe? Considering what universe means, "The universe is commonly defined as the totality of everything that exists,[1]" (see wiki universe).

 

[marcus]

Rick and Bachmeier, thanks for your responses! Bachmeier, it's a pleasure to make your acquaintance:
https://www.physicsforums.com/member.php?u=294218
What do you raise in your pesticide-free greenhouse? Sounds like a happiness+business operation.

I hope that the word universe continues to mean everything that exists, even if our local region of spacetime turns out to be only a chapter in the book. That's my personal preference, for what it's worth. We can't say how language will evolve. The language that each of us acquires and uses is just one ant in the great ant-heap of English. So we basically just wait and see what usage prevails.

 

[M. Bachmeier]

Rick and Bachmeier, thanks for your responses! Bachmeier, it's a pleasure to make your acquaintance:
https://www.physicsforums.com/member.php?u=294218
What do you raise in your pesticide-free greenhouse? Sounds like a happiness+business operation.

Happiness yes. Food & or flowers yes. Small & personal, no business) It's nutrient medium (coco bags) growing (not true hydroponics) where I collect the leach (leftover fertilizer) and use it for other plants. Extra food is donated locally. It's also a very good man cave for me to hide in during winter shutdown. I can get a nice safe (UV resistant plastic) tan during the winter without adding heat. Today the the temperature got to 21 Celsius with an outside temperature of -13 Celsius. It's very good for my health and would be for anyone else who sought out such a hobby.

If you would like more information email me or private message, as I'm sure this is way off topic.

 

[Chalnoth]

If such ideas hold will our (universe as we know it) get downgraded to a sub-universe. First Pluto then the universe? Considering what universe means, "The universe is commonly defined as the totality of everything that exists,[1]" (see wiki universe).

In my view, we should have had separate words for our region of the universe and the totality of the universe for a long time now, ever since we realized that there was a horizon. Eternal inflation is a potentially interesting way for how things might vary from place to place outside our observable region, but there are other ways this could happen as well.

 

[MTd2]

I am not fond of eternal inflation. It doesn`t have any fundamental theory to back it up and so looks like sort of put there by hand trick.

But, the conformal cyclical cosmology, as proposed by Penrose, it seems to me, can be adapted to cyclical models that includes bouncing. The adaptation would be mapping the conformal infinity as going infinitely big as going very small, like in LQC.

In fact, finding these circles might be used as a tool for LQC studies, I think.

 

[Chalnoth]

I am not fond of eternal inflation. It doesn`t have any fundamental theory to back it up and so looks like sort of put there by hand trick.

But, the conformal cyclical cosmology, as proposed by Penrose, it seems to me, can be adapted to cyclical models that includes bouncing. The adaptation would be mapping the conformal infinity as going infinitely big as going very small, like in LQC.

In fact, finding these circles might be used as a tool for LQC studies, I think.

I think you've got things reversed there. Eternal inflation has a fairly decent theoretical backing. CCC has none whatsoever, and is completely unrelated to LQC.

 

[marcus]

Eternal inflation has a fairly decent theoretical backing. CCC has none whatsoever, and is completely unrelated to LQC.

I don't think MTd2 said that CCC was related to LQC, so I don't see what point you are making by telling him that it isn't.

He also did not say that EI was related to LQC. I think he suggested that some of the analytical findings, and I would add the METHODS, that Feeney et al used might be adapted for testing LQC. It is an interesting speculative possibility which does not depend on the theories themselves being similar. What might be adapted is techniques of how you treat CMB data.

I agree with what you said about terminology: we should have had all along some different words for the whole universe and for "our part". I'm not sure if there is a model-independent definition of what "our part" is. But some distinction like
A. universe
B. observable universe
deserves to be concisely embedded in vernacular.

Personally I don't hold the "theoretical backing" for Eternal Inflation in high regard, though I grant you it exists. That is partly just a matter of individual taste---one's attitude towards the String Theory Landscape, and the superannuated chimaera of "M-theory". For me, Eternal Inflation and its "theoretical backing" has gotten kind of stale over the past 20 years. Just a subjective feeling. I believe we have seen some new thinking about inflation during the past 5 years that could generate a change of perspective on it.