Uncovering the Mystery of Quantum Foam

[marcus]

...With regards to the balloon analogy wasn't there and still is energy coming from somewhere to "fuel" the expansion ?...cos I really don't get how the universe does it. If it is left over from the big bang then to me it implies a leading edge/horizon and besides inflation shouldn't be speeding up and there shouldn't be more space being created.
...

hi spicerack, and Richard too!

you two are doing fine in exploring these basic questions
I only came into the discussion because I get enraged when i hear someone say that in LQG space is divided into little bits.
the exasperating thing is that measurements about geometry DO get discretized in LQG so there is information that one system has about another, geometrical information, that does turn out to be discrete. So it is one of these ideas that creates confusion because it is ALMOST true.
And maybe indeed in some other perfectly nice theory space is divided up into little bits! Just please don't attribute that idea of LQG. I do not think people yet have the right theory of what space and time are. I don't know how the right theory will turn out.

The big questions are not about specific theories that people are working on. The big questions are much simpler. and cannot be encompassed by asking about some particular theoryl The fact is, i am fundamentally clueless about what space is or how to think of it. I cannot answer your questions, which are fundamental questions. So I am very glad that you keep patiently asking and speculating between yourselves about it. this is even, in a sense, your job. it needs to be done so that people will be constantly reminded of what they don't know.

For example, I think important questions are like

Why is the light redshifted?

You spicerack have probably wondered. We get all this light from far-off galaxies. when u study it thru a prism u see a pattern of lines that show that it originally was much higherfrequency shorter wavelength light, because atoms like hydrogen and sodium have a signature in the lines and the pattern has been shifted. we recognize the signature of atoms but the pattern has been stretched out. Why? How did this happen?

It doesn't seem to work to try to explain it by DOPPLER. you try to put together a jigsaw of different redshifts from different galaxies and if you try to attribut the shift to a SPEED that the galaxy had when it spit out the light, then you have to put togethere this jigsaw of thousands of speeds and it doesn't work. People keep trying but no realistic picture emerges that cosmologists can accept. So we conclude that the redshift IS NOT DUE TO THE SPEED THE GALAXY HAD WHEN IT EMITTED THE LIGHT.

the picture that has emerged over 70 some years is that the redshift is due to all the distance increase that happened in the space that the light traveled thru while it was traveling

this is an extremely strange idea. you are right to question it constantly and say over and over again "How can this be?" And i cannot answer you
(not only am I not the expert authority who should answer but I also find it quite strange)

All I can tell you is that we have so far only one theory of gravity that works well, Gen Rel. that is the only one that gives really accurate answers about little things like the light-bending angle and tiny distortions of time.
And Gen Rel has no solutions for the universe except where distances are constantly increasing (or, in other case, decreasing)

this doesn't mean that Gen Rel is true. only that we don't yet have anything that works better. it doesn't mean that distances are increasing, that is merely a theoretical result of Gen Rel.

however this business of distances increasing seems to explain the redshift!

indeed it predicted it ahead of time. Gen Rel came in 1915 and the redshift was noticed around 1930 if I remember.

Now the increasing distance business in Gen Rel DOES NOT REQUIRE ANY FUEL. It is, so to speak, just how distance behaves.
Gen Rel, at most basic level, is a theory (which matches observation out to 6 or so decimal places) of how distance behaves.

It says that it is not realistic to expect the distance between two stationary galaxies to remain the same. It would take fuel to keep them the same distance from each other. If you do nothing then the distance between quietly gets larger.

and this seems to be the simplest consistent explanation of the stretched out wavelength pattern in the light of thousands of galaxies that we are all the time getting.

and yet is is a profoundly strange and almost unacceptable idea

and furthermore, since all human theories are eventually proven wrong, we know in particular that Gen Rel will eventually be replaced, so we cannot even say that this idea is certain to be true. yet there is nothing better.

you see what a problem

 

[marcus]

Have to say that as a practical matter I have very high confidence in Gen Rel and in the quantized versions of it that are emerging under the heading of LQG. I don't expect better for a long time and suspect that eventual replacements of Gen Rel will retain salient features like expansion and modeling gravity geometrically. I may sound too agonizing and plagued by doubts in prev. post, but have to emphasize lack of certainty.
On a more upbeat note, a lot of progress is being made and so on.

In another thread Moving Finger cited this Lineweaver Davis article called "expanding confusion". It is a good thing to read as a cure for people's confusions about expansion.
Here is a quote from page 18 in the "conclusions" section at the end:

" An abundance of observational evidence supports the general relativistic big bang model of the universe. The duration of supernovae light curves shows that models predicting no expansion are in conflict with observation. Using magnitude-redshift data from supernovae we were able to rule out the SR interpretation of cosmological redshifts at the approx. 23 sigma level. Together these observations provide strong evidence that the general relativistic interpretation of the cosmological redshifts is preferred over special relativistic and tired light interpretations. "

See how careful. they don't say Gen Rel is RIGHT they say that the alternative explanation that the redshift is from Doppler can be ruled out to 23 sigma confidence level.
that is, one can assume the redshift is due to stretching by expansion of space, not because one can prove it but because the only other reasonable explanation people could think of can be ruled out to extremely high statistical level of confidence (for discussion of that see the main part of the paper)

Here is a link to the "Expanding Confusion" article by Tamara Davis and Charles Lineweaver:
http://arxiv.org/abs/astro-ph/0310808

 

[wolram]

By Chronos
I resist the graininess analogy. I'm more inclined to think of it as blurriness. In my mind space and time are coordinate systems describing topological relationships between particles in the universe. I'm also inclined to think gravity is a form of quantum entanglement between particles that originated in the big bang singularity.
---------------------------------------------------------------------
WOW a whiff of fresh air, you could be right chronos, give it a couple
more years and people may look to ideas like this.

 

[marlon]

he cites a populariized non-math account by Rovelli as his source.

I think it's fine to use popularized accounts as an introduction, to get acquainted at the start, but you have to recognize that you are getting a non-mathematical impressionistic version. don't get hung up on the initial verbal description.

Sorry marcus but i find it very hard to believe that Rovelli would write an (indeed i admit) very introductory article that is basically wrong in nature. If i made any mistakes, then please do correct me but saying only that this content is wrong is a bit easy in my opinion. Besides, i really don't see why you are always talking about the non-existence of the space-granulae since it is quoted by Rovelli in the article and also in his book. Why is this wrong ? What is it that i misinterpreted about these granulae?

marlon

 

[marlon]

Sorry marcus but i find it very hard to believe that Rovelli would write an (indeed i admit) very introductory article that is basically wrong in nature. If i made any mistakes, then please do correct me but saying only that this content is wrong is a bit easy in my opinion. Besides, i really don't see why you are always talking about the non-existence of the space-granulae since it is quoted by Rovelli in the article and also in his book. Why is this wrong ? What is it that i misinterpreted about these granulae?

marlon

Could someone help me out with my questions, please ?

regards
marlon

 

[marcus]

Could someone help me out with my questions, please ?

regards
marlon

here is primer
it is old (1998) but it is the most elementary treatment I know (that is not a popularization or mere verbal description)

http://arxiv.org/abs/gr-qc/9806079
Loop quantum gravity and quanta of space: a primer
Carlo Rovelli, Peush Upadhya
11 pages

Abstract: "We present a straightforward and self-contained introduction to the basics of the loop approach to quantum gravity, and a derivation of what is arguably its key result, namely the spectral analysis of the area operator. We also discuss the arguments supporting the physical prediction following this result: that physical geometrical quantities are quantized in a non-trivial, computable, fashion. These results are not new; we present them here in a simple form that avoids the many non-essential complications of the first derivations."

MARLON, if you want to discuss LQQ, please do not try to reproduce ideas from popularized accounts and your impressions taken from other people's verbal imagery. The only way to have any technical knowledge is to assimilate a mathematical treatment, at least beginning level.

this article (Rovelli/Upadhya) is out of date, but it is the simplest technical treatment to start with. I will keep watch to see whether your ideas of LQG change. Right now our notions of it are too different to permit discourse. As long as you are talking about "granulae" or "granules" of space I do not want to try to talk with you. I suspect it would be impossible to communicate.

 

[setAI]

once again- the computational view on the issue of quantized spacetime makes all of these Zeno-esque arguments moot- when the metric is emergent from relationships you've got no problems dealing with a discrete spacetime

 

[spicerack]

sorry setAI

but could you dumb that last post of yours down for me? I would love to know what you said and mean.

Can you post to a link preferably in simple english for a simple person ?

thanks

 

[marlon]

here is primer
it is old (1998) but it is the most elementary treatment I know (that is not a popularization or mere verbal description)

Marcus, in all honesty, have you actually read this article ? I seriously doubt it.

Besides, you call my reference out of date yet this article is 5 years older ?
I mean, really, what's up ?

As long as you are talking about "granulae" or "granules" of space I do not want to try to talk with you. I suspect it would be impossible to communicate.

I am glad you ain't no politician because you sure as hell ain't got no sense for democracy. I am a bit dissapointed here. I mean, dear Marcus, posting arxiv-links and copying their content is NOT how science is done. I have noticed that everytime a topic gets difficult, you tend to back out by saying you are not an authority. Now, i have no problem with this but, then again, don't correct others if you are no specialist (and indeed you are not, you are a librarian). The intention of my intro to LQG was very much what is stated in the actual title, so stop whinning about that.

Whether or not you want to discuss this with my really is your business but please, don't be such a big baby in saying that something correct is wrong. besides you are no king, you cannot insult others by saying their 'vision' of LQG is wrong. I am trying to do something usefull here: i am trying to explain LQG, which i am learning myself. I asked you two specific questions which you did not answer (posting some arxiv-link that you did not even read is not answering my problems). So either, you really help me out or otherwise, just stop demonizing me with respect to others and stop the whinning...

regards
marlon

 

[setAI]

sorry setAI

but could you dumb that last post of yours down for me? I would love to know what you said and mean.

Can you post to a link preferably in simple english for a simple person ?

thanks

the issue here is whether spacetime has a granular quantized structure [or as Lee Smolin refers to it- an atomic structure]

the argument has been that space is granular and the there is no such thing as a truly continuous spacetime- and the other view that granularity does not exist- that spacetime IS continuous and that quantum theories are only approximations so granularity is only added to the equations to get rid of infinities and make them computable-

but the computational view makes this argument go away- because it conjectures that the metric of spacetime emerges from fundamental quantum bit relationships that yield a 'virtual' spacetime metric in which matter/energy are a back-reaction and propagate through the lattice/graph of quantum bits like a cellular automaton [actually they ARE probably a simple quantum cellular automaton- it's likely not just a metaphor]- so that distance itself is expressed as a connection between entangled quantum bits- so spacetime IS granular because the smallest unit of space and time must be the relationship between two quantum bits- [as suggested by the Holographic Principle] but this result speaks NOTHING about the potential continuity of a Euclidean space- because no such space exists!- or it doesn't exist at the level of the quantum universe that we observe because spacetime is essentially a VIRTUAL space generated by quantum computation- it certainly may be that the level of the universe where quantum bits interact [the "natural quantum computer" [black holes in nested spacetimes?] that is running the q-algorithm that generates our spacetime] is continuous in some way- but spatial metrics mean nothing at that level because space-ness and time-ness are virtually emergent from the degrees of freedom of the computations of those q-bits interacting in an orderly causal lattice- so the idea of a Euclidean space that can be infinitely divided is just an idea- QM/ Quantum Gravity [including LQG/ quantum geometry/ BH thermodynamics/ etc] and the Holographic Principle all suggest that space and time emerge from a causal matrix of discrete bits

so spacetime is not discrete per se- but the interacting bits which create the virtual spacetime and define the metric ARE

 

[Mike2]

Maybe I missed something. Are you suggesting that quantum computing is done by something that does not occupy (or is described in terms of) spacetime? I thought quantum computing was done through the means of physical objects.

The question is how does the quantum foam arise out of the structure of spacetime, or visa verse. Perhaps the structure of spacetime is a prerequisite for the formation of virtual particles. It seems obvious that you cannot have particles without a spacetime as a background in which to describe the particles. But there can be spacetime without particles since virtual particles aren't everywhere all at once, and they travel through spacetime before recombining. So there must be something inherent in the nature of space time that causes virtual particles to appear. If VP (virtual particles) have a probabilistic nature, then there must be some probabilistic nature to spacetime itself. But what are the probabilities of spacetime associated with? Is it as with Dynamical triangulation where there is a probability associated with various dimensional manifolds that are added in quantum mechanical superposition? If particles are extended objects, then they are probably submanifolds embedded within overall spacetime. Then the particles may be where the various dimensional spaces are not mixing exactly, leaving submanifolds behind in the process.

the issue here is whether spacetime has a granular quantized structure [or as Lee Smolin refers to it- an atomic structure]

the argument has been that space is granular and the there is no such thing as a truly continuous spacetime- and the other view that granularity does not exist- that spacetime IS continuous and that quantum theories are only approximations so granularity is only added to the equations to get rid of infinities and make them computable-

but the computational view makes this argument go away- because it conjectures that the metric of spacetime emerges from fundamental quantum bit relationships that yield a 'virtual' spacetime metric in which matter/energy are a back-reaction and propagate through the lattice/graph of quantum bits like a cellular automaton [actually they ARE probably a simple quantum cellular automaton- it's likely not just a metaphor]- so that distance itself is expressed as a connection between entangled quantum bits- so spacetime IS granular because the smallest unit of space and time must be the relationship between two quantum bits- [as suggested by the Holographic Principle] but this result speaks NOTHING about the potential continuity of a Euclidean space- because no such space exists!- or it doesn't exist at the level of the quantum universe that we observe because spacetime is essentially a VIRTUAL space generated by quantum computation- it certainly may be that the level of the universe where quantum bits interact [the "natural quantum computer" [black holes in nested spacetimes?] that is running the q-algorithm that generates our spacetime] is continuous in some way- but spatial metrics mean nothing at that level because space-ness and time-ness are virtually emergent from the degrees of freedom of the computations of those q-bits interacting in an orderly causal lattice- so the idea of a Euclidean space that can be infinitely divided is just an idea- QM/ Quantum Gravity [including LQG/ quantum geometry/ BH thermodynamics/ etc] and the Holographic Principle all suggest that space and time emerge from a causal matrix of discrete bits

so spacetime is not discrete per se- but the interacting bits which create the virtual spacetime and define the metric ARE

 

[setAI]

Maybe I missed something. Are you suggesting that quantum computing is done by something that does not occupy (or is described in terms of) spacetime? I thought quantum computing was done through the means of physical objects.

what is the "quantum computer" that is computing our universe? that's a dicey question like what is a string made of- or what was before the Big Bang- there are some different ideas [computational cosmology takes quantum information as fundamental and all other aspects of the universe are derived] but generally we are talking about fluctuations of the Dirac/Feynman/Pauli/et al quantum field-

but I have been thinking lately that we are looking at some sort of nested black hole framework like with Lee Smolin's CNS toy-idea or Guth's inflation field- where you have new spacetime regions expanding but the expansions are actually quantum computations in a parent universe- black holes are by definition the ultimate quantum computer- perhaps what they compute are whole cosmological wavefunctions and the resulting universes virtually emerge- supermassive black holes have the processing power and memory to spare to compute universes like ours- [there are actually theories that any quantum computer can be configured to perform infinite/universal computation] but this is just my current toy model-[I have a newer/weirder toy idea where there is only one quantum bit- a single zero dimensional pulse from off to on-and because it is the only thing it is it's own singularity- a feedback loop where it must interfere/interact with itself in an infinite number of configurations occurs- the infinite feedback echo resulting in an infinite dimensional matrix yielding the Multiverse]-

but the Computational Universe research program has been so rigerously rational and empirical- I feel that this sort of metaphysical speculation somehow diminishes the work

here is an interesting paper on black hole quantum computation and quantum foam:
http://www.arxiv.org/abs/gr-qc/0403057

 

[Mike2]

what is the "quantum computer" that is computing our universe? that's a dicey question like what is a string made of- or what was before the Big Bang- there are some different ideas [computational cosmology takes quantum information as fundamental and all other aspects of the universe are derived] but generally we are talking about fluctuations of the Dirac/Feynman/Pauli/et al quantum field-

I've been wondering if all of QM can be exressed in terms of quantum information theory. Is there an Information Theory equivalent formulation to the probabilistic nature of QM and QED and QCD, etc?

We may be talking about the same thing where spacetime itself is the quantum computer that calculates the world. The question is what gives rise the the fluctuation of spacetime? It would seem to require a quantum mechanical superposition of states to give rise to uncertainty, right? But what are the different states of space?

One thing seems certain, if there is a foam, then there is a dynamical process going on that has a time dependence. Surely this is connected with the other time dependence of space known as expansion. Expansion must be related to any spacetime fluctuations, right?

 

[marlon]

I've been wondering if all of QM can be exressed in terms of quantum information theory.

Sure it can, QIT is a child of QM. the question really is : can QIT be expressed or put into a real classical computer. Answer : YES IT CAN because all you need to be able to do is rotate some vectors and work with matrices. Who ever said QM was difficult ? Just look at the group theory part of QM : that's nothing but matrices

marlon

 

[spicerack]

jeez SetAI, if that is as dumbed down as you can make it then there might not be much hope for me.

One thing though does your theory require extra dimensions ?

cos it seems it would make it handy for when the switch is "off" for it to still be "on" somewhere else that isn't locked in 4d space. So if it did require manifolds as kind of circuits for the switches then while one was "off" another could be "on" in exactly the same place but be part of a different configuration of space as time has moved on even if it was imperceptiible to observation and allow for different particles to change shape without changing place and seemingly occupy 2 spaces at the same time.

did that make sense if it didn't just ignore me and carry on cos with a bit more visualising i'mpretty sure i could see what you guys are on about

thanks heaps though you 2Mike

 

[setAI]

jeez SetAI, if that is as dumbed down as you can make it then there might not be much hope for me.

if you lived in a 16 bit video game- your world and everything in it will be 2D pixelated sprites [or rather a discreet matrix of possible pixel values from the program]- but the computer hardware running the game software isn't necissarily made of 2d pixels is it? so while it is true that your 16 bit world is granular this granularity is emergent and you cannot say that the universe/computer is granular itself-

One thing though does your theory require extra dimensions ?

computational cosmology agrees with the holographic principle- you start with bits of information with only 1 degree of freedom [on/off] whose causal connections determine the degrees of freedom/dimensionality of the space- so LESS dimensions are fundamental- but probably any number of dimensions can emerge from the computation- in fact since quantum logic gates have two inputs and two outputs four dimensions arise naturally in computational cosmology!

 

[nightcleaner]

if you lived in a 16 bit video game- your world and everything in it will be 2D pixelated sprites [or rather a discreet matrix of possible pixel values from the program]- but the computer hardware running the game software isn't necissarily made of 2d pixels is it? so while it is true that your 16 bit world is granular this granularity is emergent and you cannot say that the universe/computer is granular itself-



computational cosmology agrees with the holographic principle- you start with bits of information with only 1 degree of freedom [on/off] whose causal connections determine the degrees of freedom/dimensionality of the space- so LESS dimensions are fundamental- but probably any number of dimensions can emerge from the computation- in fact since quantum logic gates have two inputs and two outputs four dimensions arise naturally in computational cosmology!

Hi SetA1
This sounds interesting. Could you link to a primary source on computational cosmology? Who are your best authors on the subject? Who are you reading now? I believe I recall reading somewhere about our universe being a two dimensional holographic image on the event horizon of a BH. Is this part of what you are talking about?

Thanks,

nc

 

[spicerack]

computational cosmology agrees with the holographic principle- you start with bits of information with only 1 degree of freedom [on/off] whose causal connections determine the degrees of freedom/dimensionality of the space- so LESS dimensions are fundamental- but probably any number of dimensions can emerge from the computation- in fact since quantum logic gates have two inputs and two outputs four dimensions arise naturally in computational cosmology!

umm... so the simple answer is no it doesn't require extra dimensions but yes the theory has enough freedom in it to accommodate them

so now I'm hung up on "causal connections". Is that what trips the switches or what the switches are embedded in or am I off on a tangent again ?

and i very much appreciate the patience you have all shown. Thanks

 

[Kea]

...in fact since quantum logic gates have two inputs and two outputs four dimensions arise naturally in computational cosmology!

Yes, setAI, exactly! Only you make it sound so simple that I'm not sure many people here will suddenly be converted...there is a very deep sense in which
this explanation of four dimensionality is true.

Remember that quantum computation can be modeled by anyonic topological systems described mathematically by Jones polynomials...well, to be more accurate, modular functors...

Cheers
Kea

 

[setAI]

Hi SetA1
This sounds interesting. Could you link to a primary source on computational cosmology? Who are your best authors on the subject? Who are you reading now? I believe I recall reading somewhere about our universe being a two dimensional holographic image on the event horizon of a BH. Is this part of what you are talking about?

Thanks,

nc

the foundation of the computational universe is Dirac and Feynman- Marvin Minsky's Cellualr Vacuum- right now Seth Lloyd is blowing my mind [he's good at that] check the "Third Road" sticky for some interesting papers

David Deutsch and Sir Martin Rees are getting into this action lately as well

 

[nightcleaner]

Thanks again. I saw the Feynman book but havn't read it yet. Checking on the others.

nc

 

[spicerack]

Remember that quantum computation can be modeled by anyonic topological systems described mathematically by Jones polynomials...well, to be more accurate, modular functors...

How could i forget ?

so the proof is in the maths but without the maths what is a simple analogy that might be apt ?...a black hole as a computer spitting out info that constitutes a hologram reality projected onto a 4d screen like a moving graphic simulates 3d on a 2d computer screen ?

It still leaves a first cause and lasting effect open to speculation though doesn't it and where do we fit in ?

Are we just ghosts in the machine ?

I have so many questions yet so little understanding of the answers, should I even bother asking ?

cheers

 

[Kea]

Hi to spicerack

...so the proof is in the maths but without the maths what is a simple analogy that might be apt?...a black hole as a computer spitting out info that constitutes a hologram reality projected onto a 4d screen like a moving graphic simulates 3d on a 2d computer screen?

It still leaves a first cause and lasting effect open to speculation though doesn't it and where do we fit in? Are we just ghosts in the machine?

I have so many questions yet so little understanding of the answers, should I even bother asking?

Of course one should bother asking! What are we here for, after all? I like your image of black holes making holograms. As far as I see it though (but others may disagree) there's a big problem with this image - it all happens in some classical spacetime. This is the big conceptual prejudice that we need to get rid of. Quantum computation doesn't happen in an aether or anything like that. It generates our idea of spacetime, as setAI has been saying. Moreover, the classical reality is highly derived, relying as it does on a very large number of observations.

So, one needs to understand what an observation is...and once one recognises this fact one can either throw one's hands up in despair (as I did many times) or one can reluctantly accept that one might need to learn an awful lot of mathematics, because without it one's quantum intuition simply isn't good enough.

Regards
Kea

 

[Chronos]

Kea, that was a profound statement. But it does not stop you from seeking a better solution, does it? Have you published a paper yet? I would be very interested in hearing your thoughts - which are provacative. Despite my weakly supported arguments against Wiltshire, I admire his imagination and courage. I look forward to his future papers.

 

[Kea]

But it does not stop you from seeking a better solution, does it? Have you published a paper yet?

To the second question, if we restrict our consideration to this subject, the answer is technically no. Not for want of trying.

You are quite right about trying to seek better solutions. I wish I was better at thinking up simple analogies. Like the rubber sheet for GR: it gives one a completely wrong impression of the subject, but it's helpful anyway.

How about penguins? Think of a penguin. We can't understand what a penguin is without knowing about the existence of the ocean, and sandy beaches and fish and so on. But this requires a complex reality created out of a very large number of observations. So penguins are largely classical creatures. A penguin Bob either exists, or does not exist. Quantum penguins on the other hand, like quantum black holes, operate according to a much more Adamsian logic.

All the best
Kea

 

[Kea]

...

These prejudices are so invasive that they pervade even the best work in LQG. Picture a Black-Holes-Generate-Baby-Universes scenario...always described from the viewpoint of a metametaobserver, which the theory says cannot possibly exist!