Question on Smolin's theory on Black Holes and new Universes

[Tanelorn]

Smolin has a theory that black holes in our Universe result in new Universes. He says Universes that are capable of creating black holes get to produce more Universes etc.

http://www.space.com/21335-black-holes-time-universe-creation.html

I was reminded of Smolin's ideas by this recent article:

http://www.mnn.com/earth-matters/sp...ged-from-a-black-hole-in-a-higher-dimensional

So I was wondering is Smolin's theory regarding the importance of black holes becoming more mainstream? Presumably it could never be proved? At least Black Holes seem to be a partition between our U and somewhere else.

 

[Drakkith]

I'd say it's about as mainstream as Santa powering his sleigh with depleted anti-uranium.

But seriously, I'd probably look at it as simply an interesting but unlikely possibility.

 

[Doug Huffman]

Fitness landscapes and anthropic cosmologies are common topics not only at the Perimeter Institute where Smolin is associated, but also of Smolin's foil, Leonard Susskind at Stanford U. with his anthropic string theory landscape.

Smolin predicted a maximum mass of neutron stars that has been verified but not yet Popper falsified. How that bears on your question of his credibility is quite up to the observer.

As to 'partitions', Susskind defends and explains the mulitverse, that he calls Megaverse, quite well, enough that I understand it.

 

[Tanelorn]

Thanks Doug, I didn't know much of that. Coincidentally I think I also independently thought of the words partition and megaverse to describe the same ideas as Susskind.

Thanks Drakkith, I was mainly trying to find out how likely other Cosmologists thought this is, compared to say branes or string theory or wormholes and other theories. If anything in our U can create a partition and gateway to somewhere else then from what I understand it a BH would have the best chance.

 

[Chronos]

In Smolin's original cosmic natural selection hypothesis, circa 1992, he predicted a maximum neutron star mass of about 1.6 solar. While larger mass candidates were discovered over the years, the error bars remained large enough to accommodate the hypothesis until 2010; http://arxiv.org/abs/1010.5788, Shapiro delay measurement of a two solar mass neutron star. Smolin hedged his bet in 2004 to 2.5 solar masses; http://www.nat.vu.nl/~wimu/Varying-Constants-Papers/Smolin-Physica-2004.pdf, Cosmological natural selection as the explanation for the complexity of the universe. As far as I know he still holds to that prediction. At least in my mind, the original conjecture has been refuted.

 

[marcus]

Fitness landscapes ... are common topics ...
Smolin predicted a maximum mass of neutron stars that has been verified but not yet Popper falsified. How that bears on your question of his credibility is quite up to the observer.
...

Doug, your mentioning fitness landscapes is the key thing. What distinguishes Smolin's idea is not that gravitational collapse may rebound "out the bottom" and create a new spacetime region (a form of "reproduction" :w )
A number of physicists have proposed/considered the idea that (at least above some critical mass) a black hole collapse may result in a new spacetime region. At the present state of things we can't KNOW what happens instead of the formation of a singularity but it's not uncommon for quite mainstream people to doubt the formation of a classical singularity and to consider quantum gravity effects may cause a rebound (either back in our faces or out the back door, so to speak.)

Your point about fitness landscape highlights what was original about Smolin's 1992 proposal. He suggested that reproductive fitness could explain some of the values of physical constants (ratios of masses of various particles, ratios of forces to each other, the constants in the laws of physics).
If the constants could slightly MUTATE when a new region issued from collapse, then the universe would consist predominantly of regions where the laws and constants of physics were favorable for reproduction

And so if one assumed we find ourselves in a fairly typical part of the universe we should be able to PREDICT some of the constants of the laws of physics by figuring out which values of the constants e.g. favored stable atoms of carbon and oxygen (because their molecules help gas clouds condense to form stars by radiating away heat, and so allow more stars and eventually more massive collapses.)
The originality of the 1992 "Cosmic Natural Selection" (CNS) proposal was that it was NON-ANTHROPIC. It had nothing directly to do with life or humans or observers etc etc. It offered to explain features of the Standard Models of particle physics and of cosmology by reproductive fitness.
The values of the constants are such as would place our region on a hilltop in the reproductive fitness landscape. A local maximum for the birthrate of viable offspring regions.

I would say that collapse leading to rebound is a MAINSTREAM idea, and you would find 100s of researchers willing to take that seriously as a reasonable outcome of gravitational collapse. It is one of several ideas of what might actually happen (instead of formation of a "singularity", which is more a symptom of failure or breakdown of the classical theory). It is important not to confuse this with Smolin's idea. His idea was, assuming you do get new regions budding off from gravitational collapse, that the physical constants might evolve and might thereby be predictable.

That's a lot bolder as a proposal. The best one can say is that it does seem to be falsifiable, as you indicate. One can try to find physics constants which, if significantly varied, like 5 or 10 percent (?) would this degrade the ability of clouds to radiate waste heat and massive stars to form and eventually collapse? Or at least would small variations like that NOT cause those abilities to increase? (that would be really bad for the idea!)
There should be a lot of bold risky proposals for why the laws of nature are what they are, and not something different. I expect we will be seeing more such proposed as physics progresses and asks deeper questions. Offering possible explanations for the laws and constants could become increasingly part of the mainstream. We'll see :)

 

[marcus]

BTW That new book The Singular Universe that Smolin coauthored with Roberto Unger seems to be on the point of release. Amazon is taking advance orders:
https://www.amazon.com/dp/1107074061/?tag=pfamazon01-20
I looked up "cosmological natural selection" in the book's index and it says that is discussed on pages
454-460, 464, 499, 525, and 527-528.

The book is published by Cambridge University Press. I'll check the Cambridge UP website to see if there is more information on it.
http://www.cambridge.org/us/academi...-and-reality-time-proposal-natural-philosophy

The book has nearly 600 pages (several ideas are discussed about how laws of nature can have evolved, obviously it is not solely about CNS). CUP is pricing it at around $30, which kind of surprised me. They must expect it to appeal to a wider audience than just academics.

the Cambridge Press website let's you browse the book, TOC, sample chapter selections, index etc.

 

[Tanelorn]

Thanks Marcus for clarifying the distinction, I was not aware of that. Both the collapse leading to rebound (to a new U?) and Smolin's theory have a certain elegance, not that that means anything of course.

I would be very interested in learning how well this, and other speculative theories are accepted. Perhaps some kind of a ratings system amongst Cosmologists would help part timers know which one theories to take more seriously?

 

[marcus]

Thanks Marcus for clarifying the distinction, I was not aware of that. Both the collapse leading to rebound (to a new U?) and Smolin's theory have a certain elegance, not that that means anything of course.

I would be very interested in learning how well this, and other speculative theories are accepted. Perhaps some kind of a ratings system amongst Cosmologists would help part timers know which one theories to take more seriously?

If I were a professional cosmologist, doing research, I would take those theories seriously which were relevant to my specialty, and had not been disproven. If I was not studying the very start of expansion and how we can learn about it, I would not bother to make a serious evaluation.
I would not be interested in answering the "big questions" I would focus on ideas that had a bearing on my research specialty.

So, for researchers with a legitimate interest in bounce cosmology or in NONSINGULAR cosmology generally (where there is something besides a "singularity" at the start of expansion) there are special sessions at the international conferences where they can get together and present their papers and discuss, and there are REVIEW articles that survey the different models and approaches to modeling the start of expansion (and the conditions preceding and around that).

I don't think I can give you any guidance about what YOU PERSONALLY should "take seriously" or not. If you were doing research in some type of bounce cosmology, you could publish in peer review professional journals on the same basis as other mainstream research--i.e if the quality met standards.
You could deliver your papers at mainstream international conferences, at the appropriate parallel sessions, on the same basis as other--i.e if your research was up to standard. You could find other bounce cosmology specialists to argue with, about your various different approaches, and so on.

But if you are not already involved I don't see any basis on which I could advise you. Why should anybody be more interested in this line of cosmology research than in, say inflation theories, or CmB interpretation, or galaxy-redshift counts as a key to structure, or dark matter distribution, or galaxy formation(!), or ages of star populations,...?

Personally I find the mainstream research classified as "quantum cosmology" (which for the most part is quantum bounce cosmology) intensely fascinating--so I follow it with fairly close attention even though I have no career interest (I'm retired.)
I'll get you a link to the QC papers since 2009, ranked by number of citation (a rough measure of importance in the QC category) to satisfy any curiosity, you can read the titles of the papers and sample abstracts here and there if you wish.
But I cannot advise you. It would be extremely pretentious of someone to say "do be interested" or "don't be interested", fatuous even.
You are or you aren't. If someone is, and is able to read the technical literature, I can suggest papers.

I'll get that QC link. It is to the Stanford-SLAC research data base, using keyword "quantum cosmology"
This is "quantum cosmology" since 2009, Inspire search:
http://inspirehep.net/search?ln=en&ln=en&p= "quantum cosmology" and NOT d 1900->2008&of=hb&action_search=Search&sf=&so=d&rm=citation&rg=25&sc=0 (750 found as of 30 Nov 2014)

You can see the QC research output is on the order of 10 papers per month, roughly 120 per year.
I checked and roughly half are in the Loop QG approach and the other half are in various other approaches to quantum gravity and quantum cosmology. And I see no compelling reason to take such details (of rates and percentages) seriously as if they indicated something with longterm validity or relevance. Before year 2000 the Loop QG annual share was roughly zero, now it is 50%, other approaches percentage shares have changed as well during that time.. Research emphasis changes.
Researcher interest shifts.

 

[marcus]

Still, that said, if you want to look at a review article about bounce cosmologies that survey the rebound ("no-singularity") models of the start of expansion, tell me. I'll try to find something along those lines. Maybe other people will help find a "bounce cosmology" review article, or a "non-singular" cosmology review. I have a dim memory of seeing one by a Brazilian physicist named Pereira, a few years back. Not sure. It was a while ago. Something is bound to turn up if you really want to find one. :w

 

[Chronos]

Yes, that is an interesting question. The consensus is often viewed as the latest SciAm or Nature article by an authority deemed notable by the popular press.

 

[marcus]

It's so important to distinguish between the (fairly widespread) idea of gravitational rebound at extreme energy density and the (rather exceptional) idea of the evolution of natural laws and constants by reproductive success. In any case one's subjective "belief" or opinion about "likelihood" is not so important, what counts is the empirical evidence that eventually piles up and what gives the simplest best fit.
To illustrate the ongoing research on quantum bounce cosmology, here's a paper by some physicists at University of Barcelona that just appeared last week:

http://arxiv.org/abs/arXiv:1411.7611
Viability of the Matter Bounce Scenario
Jaume de Haro, Jaume Amorós
(Submitted on 27 Nov 2014)
It is shown that teleparallel F( T ) theories of gravity combined with Loop Quantum Cosmology support a Matter Bounce Scenario which is an alternative to the inflation scenario in the Big Bang paradigm. It is checked that these bouncing models provide theoretical data that fits well with the current observational data, allowing the viability of the Matter Bounce Scenario.
9 pages. Communication to the ERE2014.

To repeat this is to know about, one of the competing types of bounce model, not to believe in :)
this type of bounce was pioneered by a prominent former string theorist, Robert Brandenberger (McGill U. , Montreal), who has gotten over into bounce cosmology. You can see a bunch of references to him and other Montreal people in the above paper's bibliography.

 

[Tanelorn]

Thanks Marcus. Does black hole collapse and then bounce mean an all new Universe with our Universe continuing on? Or is bounce the scenario that I remember from decades ago where our whole universe reverses and collapses to a singularity creating a whole new Universe?

 

[marcus]

Thanks Marcus. Does black hole collapse and then bounce mean an all new Universe with our Universe continuing on? Or is bounce the scenario that I remember from decades ago where our whole universe reverses and collapses to a singularity creating a whole new Universe?

At this stage of the game the researchers are developing different models of collapse (BH or entire universe collapse) that do different things. Our role is not to believe this or that model but to be interested in them enough to learn a little bit about the various ones. Rovelli has been working on a model of BH that does not make a new region of spacetime. The bounce causes a gammaray burst right here in this universe, somewhat like a supernova explosion. It is greatly delayed by the gravitational time dilation in the intense gravity at the core. That is interesting because we might SEE such explosions, from BH that formed a long time ago and have finally reached the bursting point. It is not likely any such things, if they exist, are near enough to hurt us.

Many other LQG researchers have worked on a BH collapse model "with our universe continuing on" like you said, where the bounce creates a new spacetime region.

BH collapse and "Big Crunch" are two different trains of thought. You mention recalling discussion of how an entire universe might stop expanding and slowly begin to contract and eventually collapse. That is theoretically possible---it is different from a BH collapse (which is localized)---and such a global collapse may have resulted in a bounce and been the beginning of our expanding universe. That is an important feature of Loop Quantum Cosmology (Lqc) and there are hundreds of papers by many people studying that. Ooops, wife calling, have to go help with supper! Back later

 

[marcus]

Thanks Marcus. Does black hole collapse and then bounce mean an all new Universe with our Universe continuing on? Or is bounce the scenario that I remember from decades ago where our whole universe reverses and collapses to a singularity creating a whole new Universe?

Tanelorn I guess the answer to both your questions is YES. For a substantial number of researchers (I don't know exactly how many) BH collapse does mean our universe continues on, we just see a conventional BH horizon (with maybe a little Hawking radiation---a slow evaporation) but inside, at the center, instead of a singularity there is a bounce creating a new expanding region of spacetime. There are variations on that theme.

And your second question was really about whole universe collapse, not BH collapse. There too, the formation of a singularity is avoided by quantum effects which kick in at extreme density (according to Loop QG, and ,it seems, some other versions of QG) causing gravity to repel briefly at that extremely high density, so there's a bounce and the universe re-expands. So your second question is basically Yes also. You heard right. Some people might not want to call the expanding phase "a whole new universe". You could think of it as the same universe, first in a contracting phase and then expanding.
In between a bounce at extremely high density, in which it is possible that all structure, all traces of the past, are wiped out.

It has been a rather intense day and I'm kind of wiped out myself. I'll return to this tomorrow and hope to say things more clearly.

 

[Doug Huffman]

I am about 50 pages into 'Singular Universe' and the concept of other than one universe is disparaged.

 

[Tanelorn]

Thanks Marcus. I was mainly trying to understand the term bounce. From what I now understand bounce is the creation of a new Universe from either the creation of a Black Hole, or the reversal and collapse of our entire Universe into a black hole. Why do they call this bounce?

 

[marcus]

Thanks Marcus. I was mainly trying to understand the term bounce. From what I now understand bounce is the creation of a new Universe from either the creation of a Black Hole, or the reversal and collapse of our entire Universe into a black hole. Why do they call this bounce?

That's a good question because it reveals an obstacle to understanding which could be bothering other people as well.
Bounce refers to a phenomenon that people discovered when they quantized GR and were surprised to see that the quantum correction terms that came in with quantizing the classical theory of gravity and became dominant at extreme energy density and short distance actually counteracted the attraction and made gravity repel.

It is somewhat analogous to the "nature resists being pinned down" Heisenberg Uncertainty Principle which says if you try to confine a particle to an extremely narrow range of position it will acquire a wide range of momentum. If you try to pin it down as to position it will be wildly zooming this way and that way. And if you try to be extremely certain about its momentum you start losing your grip on its whereabouts.

The bounce is kind of a HUP applied to gravitational collapse. But note that people have COMPETING PROPOSALS for quantizing gravity at extremely high density. However there one can see a kind of convergence among several different models. Brandenburger's "matter bounce", and the Loop approach, and various offshoots I can't keep track of, various "modified gravity" or "teleparallel" models show the same general feature: in collapse as density gets very high at some point geometry resists being infinitely pinned down and gravity repels.

This doesn't mean that it has to create a new region of spacetime! In many models it does do that, but in Rovelli's treatment a black hole collapse blows up! You know about gravitational time-slowing. To an outsider the explosion may be delayed by billions of years so we don't see it. The collapse just looks like a conventional classical black hole. But if you could live long enough to witness it, it would eventually explode in our universe (blow up "in your face", so to speak). That too is a bounce so the quantum GR bounce does not imply creation of a new spacetime region, not in every model.

Rovelli has written papers about the cosmological bounce, where the universe is in an expanding phase which was preceded by a contracting phase.
There seems to be no contradiction. If our universe stays around, then according to his proposal a BH (local) collapse bounces and blows up in our universe (like a supernova or GRB). If our universe sometime in future enters contracting phase and does not stay around, then it is a global or total collapse, which bounces and goes from contracting phase to expanding phase.

AFAIK a BH model bounce can either create an explosion (in our distant future) or a new region. I'm interested in learning more about either type of model. So "bounce" per se doesn't specify one or the other.
On the other hand, when you look at cosmology, there's a remarkable convergence: an increasing number of researchers have gotten interested in models where you can work back in time and find that our start of expansion is actually a rebound from an previous contracting phase of the same universe.

 

[marcus]

I am about 50 pages into 'Singular Universe' and the concept of other than one universe is disparaged.

I'm delighted you got such an early copy! Last time I looked it had not come on the market yet and both Amazon and the publisher (cambridge university press) were taking "advance orders". Did you qualify for a review copy? You may have other reviews of other books online, in that case. :w

In case anyone hasn't browsed the book online yet, and wants to:
https://www.amazon.com/dp/1107074061/?tag=pfamazon01-20

I mentioned earlier:
I looked up "cosmological natural selection" in the book's index and it says that is discussed on pages
454-460, 464, 499, 525, and 527-528.

About "disparagement" I suspect (not having read the book) that the key idea is that "good" science should be about nature as a causal whole---the universe that we live in, and experience, and are a part of.
Any multiplicity should be part of understanding, explaining, predicting OUR universe.

what is disparaged I would guess is where "multiverse" or "megaverse" is a vague verbal excuse for "bad" science, and excuse for giving up on the empirical tradition and the quest for adequate reasons for what we experience of this nature, this interconnected causal unity, this universe.

And so the Singular Universe book would happily include the CNS many-budded, many branching, picture because it EXPLAINS why the constants like alpha = 1/137 are what they are. The fine structure constant 1/137 is something we experience because it determines what chemical elements and what chemical reactions and compounds comprise our world. It is good science to ask why alpha is 1/137 rather than 1/100 or 1/150, and good to propose explanations for how that happened. CNS natural selection may be wrong, but it is a brilliantly simple attempt to explain that.
So it is "good" science (I would guess in the value perspectives of this book) EVEN THOUGH superficially the singular many-budded evolutionary universe of CNS visually RESEMBLES the causally disconnected multiplicity of natures with unexplained random laws to which defenders of a failed theory cling as consolation and excuse for their inability to explain the world we live in.
CNS may eventually be proven wrong, but its resemblance to what is usually meant by "multiverse" is only at a superficial level.

 

[Doug Huffman]

I pre-ordered the p-book in August when it was promised on 30 Nov by AmaXon. Yesterday I got irritated and got the KINDLE e-book and canceled the p-book order. If it is a significant book than I can get the p-book to scribble in. Already I am irritated at the clumsy access to the footnotes.

 

[Tanelorn]

Marcus said, "On the other hand, when you look at cosmology, there's a remarkable convergence: an increasing number of researchers have gotten interested in models where you can work back in time and find that our start of expansion is actually a rebound from a previous contracting phase of the same universe".

I think back in the 70s I was reading about a cyclic Universe model with repeat cycles of expansion and collapse. Then I never heard much about it again until recently when I learned about the term bounce. I do like the elegance of each and every black hole being a partition from our own Universe, thus creating a new space time similar to our own. Smolin's idea is even more elegant. When matter falls into a BH, causing its mass to increase, perhaps that would manifest itself as something like dark energy in the other U? Perhaps it is possible to imagine an almost infinite number of Universes with many branches, sub-branches and sub-sub-branches etc?

I think I prefer an approach like Smolin's to explain our fine tuned U, rather than the brute force random Universe approach where nature has to create complexity (eg. life) by trial and error.
ie. Billions of planets of different sizes and types, orbiting billions of stars of different sizes and types, formed in billions of galaxies of different sizes and types, existing in billions of super clusters of different sizes and types ... existing in billions of universes of different sizes and types ... existing in Billions of Multiverses of different sizes and types ... existing in Billions of Megaverses (my name for all possible Multiverses) of different sizes and types ... and all without a first cause?

It really is to much take in especially at this later hour.

 

[enorbet]

Why did you have to throw in "... and all without a first cause" ? It is an exercise in futility and will only diminish your ability to understand events that have and CAN have any observable evidence, at the very least with our present technology. The technology that even theoretically could "go deeper" is so far beyond the current state that if it ever occurs you can rest assured it is a safe bet that our grandchildren will have been long dead.

 

[Tanelorn]

Because I think it is important to realize philosophically that for what every clever theory we have thought of so far, it is still possible to ask, "Well what caused that?". For me it is always the elephant in the room and I do not know how to resolve it. It is not intended to mean any kind of creator either because it still applies.

 

[marcus]

Because I think it is important to realize philosophically that for what every clever theory we have thought of so far, it is still possible to ask, "Well what caused that?". For me it is always the elephant in the room and I do not know how to resolve it. It is not intended to mean any kind of creator either because it still applies.

I think the researchers in cosmology would readily acknowledge that. Everybody knows one can always ask Ultimate Questions that are not ready to be explored empirically yet, like
"Why does existence exist?". To a scientist who wants to understand the world we see and live in and are a part of, ultimate questions like that are, on the whole, not very interesting.
So they are not the huge unacknowledged ELEPHANT IN THE ROOM. That is a poor metaphor because everybody can see and acknowledge the Big Questions that are for the moment uninteresting. Everybody knows you can, if you want, give up trying to understand and predict observable stuff and if you want you can worry about "why does existence exist". It is more like the COCKROACH in the room rather than the elephant. The cockroach everybody would acknowledge is there but nobody thinks is important enough to bother with. Because questions gain importance in science when they are ripe to be answered. When they are still unripe (like Enorbet said, not even ready for our grandchildren) they just sit on the back shelf in the cupboard and wait. Good scientists have an instinct for what problems are ripe to work on---what is deep but not too deep.

So I guess we have a different perspective on super-deep ultimate questions, Tanelorn. Which is for sure OK! People have different perspectives. I am very interested in progress being made in understanding the start of expansion. What was there instead of an imaginary "singularity", what physical conditions, what was really happening instead of the "Big Bang", and how did it work.
My interest is not because it answers ultimate questions of Existence. (That is hype.) I just want to know how it worked and how we can test ideas by observing stuff in this universe we are part of. If it happens that a good theory says there was a BOUNCE, well OK I am not interested where that contracting prior phase came from. Not right now. Little steps. I just want to see one thing at a time explained.

Today a paper came out that I think is very good. It joins the Bounce idea with the standard cosmic model called LambdaCDM. So it merges or bridges two major fields.
And it also in a sense merges two schools of thought about the Bounce---the two authors, one is from the Brandenberger (McGill U, Montreal) group and one is from the Ashtekar (Penn State U) bunch, now postdoc at LSU. So the so-called "matter bounce" on one hand and the LQC "loop bounce" on the other. they are putting their bounce ideas together and bridging to the standard LCDM model. Good exciting stuff, and no one DREAMS this has anything to do with answering Ultimate Questions!
:D. It's about understanding the start of our early universe expansion which we have huge amounts of observational data on, that need to be put together and understood.

So basically my perspective is, I suspect, similar to Enorbet's, just that he expressed it differently.

 

[marcus]

Tanelorn! I'm so glad my kind of brash expression did not offend. Let me post the paper about LambdaCDM bounce in case it interests you:
http://arxiv.org/abs/1412.2914
A ΛCDM bounce scenario
Yi-Fu Cai, Edward Wilson-Ewing
(Submitted on 9 Dec 2014)
We study a contracting universe composed of cold dark matter and radiation, and with a positive cosmological constant. As is well known from standard cosmological perturbation theory, under the assumption of initial quantum vacuum fluctuations the Fourier modes of the comoving curvature perturbation that exit the (sound) Hubble radius in such a contracting universe at a time of matter-domination will be nearly scale-invariant. Furthermore, the modes that exit the (sound) Hubble radius when the effective equation of state is slightly negative due to the cosmological constant will have a slight red tilt, in agreement with observations. We assume that loop quantum cosmology captures the correct high-curvature dynamics of the space-time, and this ensures that the big-bang singularity is resolved and is replaced by a bounce. We calculate the evolution of the perturbations through the bounce and find that they remain nearly scale-invariant. We also show that the amplitude of the scalar perturbations in this cosmology depends on a combination of the sound speed of cold dark matter, the Hubble rate in the contracting branch at the time of equality of the energy densities of cold dark matter and radiation, and the curvature scale that the loop quantum cosmology bounce occurs at. Finally, for a small sound speed of cold dark matter, this scenario predicts a small tensor-to-scalar ratio.
14 pages, 8 figures

The small tensor to scalar ratio is important to get right in the aftermath of the BICEP-2 versus Planck controversy. BICEP measured a high value of the ratio, and recently Planck had a conference where they showed evidence that the polarization BICEP found could be explained by the orientation of dust particles in the foreground, in our galaxy's magnetic field. So they in effect scaled back the tensor-to-scalar ratio. Now Cai and Wilson-Ewing are being careful that when they run a more realistic LCDM start of expansion they should get a low value of that ratio.
Little details. Little little little details. Two postdocs. Got their degrees in 2010 and 2011. I like both of their past work. Very happy with this present collaboration!

 

[Tanelorn]

Thanks for thoughtful reply Marcus. I really like observational and theoretical astronomy also.

I thought about dust affecting polarization, being in RF myself. I think we have to be careful about reading too much into a radio signal.

But the ultimate question for me has to be, either there is a first cause, or there is not a first cause. And if no first cause then how do we get around that?

Perhaps there is an infinite number of Smolin type, increasingly fine tuned spacetimes before our U, or perhaps there was a first cause beyond which there was nothing whatsoever at all. Can a state of true nothingness even exist? Perhaps philosophical analysis can help direct our search for understanding our existence? It may be possible to think of all possible cosmologies and rule the unlikely ones out?

Never any offence from you marcus, I very much respect the work you put in.

 

[marcus]

Well that is a clear concise honest statement of a concern. As far as I know there is no evidence that existence had a beginning.
It seems simplest (given we have no evidence of a beginning) to assume it always was.

What's interesting, I think, is to learn of the changes it seems to have undergone. As people work back, step by step.

I like the simple concise way you describe one possible way it could have "always been"
You say:
"infinite number of Smolin type, increasingly fine tuned spacetimes before our U"

I don't know of any reason to rule that out, as one possibility for "it always was".
But I have to remind myself that we don't yet have proof for that picture, it is just a possibility, and there may be some other "always was" scheme that hasn't been thought of yet, and that someone will think up a couple of years from now. :w

 

[Garth]

One use that the CNS theory is put to is to explain the anthropic coincidences.

As has been said above, the theory predicts that the majority of universes 'evolve' so the

constants of physics were favorable for reproduction.

As universes 'reproduce' through the apparent singularities at the heart of black holes, universes evolve to maximise the number of black holes they contain.

It is just a coincidence that the conditions to maximise black hole formation in a particular universe (if Smolin is correct) happen to be the same as those required for life.

A bit of a coincidence that.

Just a thought,
Garth

 

[enorbet]

Greetz
I meant no offense and didn't assume you meant Creationism, Tanelorn, and certainly I am not exempt from boundless curiosity. I'm simply trying to exert more discipline on myself to apply leverage where it can hopefully have more effect ie - stick to what we can observe. At the moment of reading your post I just felt like I was enjoying yogurt when suddenly you mentioned a juicy cheeseburger:)

Since then Marcus has made it altogether worse (better?) by bringing up sizzling bacon :D Thank you, marcus, for that link. Fascinating stuff!

 

[Tanelorn]

enorbet thanks for reply. I do enjoy an unusual a la carte. ;)

I found a wiki piece on bounce, but it doesn't specifically mention the collapse of black holes resulting in new universes.

http://en.wikipedia.org/wiki/Big_Bounce

 

[Tanelorn]

As far as I know a state of true nothingness is the only state which does not require a first cause. For all other concepts I can ask, well what caused that? The next question is, how can we go from a state of true nothingness to any other state, because this step is infinite?

Seasons greetings all.

 

[julcab12]

As far as I know a state of true nothingness is the only state which does not require a first cause. For all other concepts I can ask, well what caused that? The next question is, how can we go from a state of true nothingness to any other state, because this step is infinite?

Seasons greetings all.

... Maybe the underlying layer of causation/locality could be relational and transformative. OTH. I could treat nothingness as infinity's evil twin.

I like the simpler version that marcus stated. "I think, is to learn of the changes it seems to have undergone.."

 

[Tanelorn]

I wonder what would happen in a Smolin black hole Universe model when two black holes merge?

http://www.nytimes.com/2015/01/08/s...les-dance-toward-an-explosive-union.html?_r=1

 

[Chronos]

Good question! Black hole evaporation would be another issue. Does causal disconnection insulate 'baby' universes from the fate of 'mommy'? Such questions wander beyond my comfort zone. I view it as a backdoor 'multiverse' version of reality.

 

[PeterDonis]

I wonder what would happen in a Smolin black hole Universe model when two black holes merge?

As I understand the model, from the point of view of any event in the baby universe, events in the "spawning" universe are all in the past. That includes the events involved in a black hole merger. From the viewpoint of the baby universe, the "singularity" inside the black hole that spawned it is still one singularity--one spacelike hypersurface that marks the past boundary of the baby universe. The only difference if that black hole merges with another one is that the event horizon surrounding that singularity, in the "spawning" universe, is shaped like a pair of trousers instead of a cylinder (if we imagine a space-time diagram in which time is vertical and we suppress one spatial dimension so the cross section of the event horizon is a circle instead of a 2-sphere). But all that is in the past of the baby universe.

 

[PeterDonis]

Does causal disconnection insulate 'baby' universes from the fate of 'mommy'?

As I understand the model, yes; the baby universe, like any event inside the event horizon of the black hole that spawned it, is causally disconnected from events in the exterior region in the original universe, including "heat death" or anything else. The only caveat to this that I'm aware of is that the "baby universe" model, AFAIK, doesn't work if the original universe recollapses in a Big Crunch, because in that scenario there are no true event horizons in the original universe; every timelike or null path ends up in the Big Crunch singularity, so there is no "room" for baby universes to spawn, so to speak. But this is getting outside of my comfort zone too; I don't know what other kinds of speculative models have been considered, so there may be some that get around this somehow.