A big bang in an infinite flat universe?

[Martin]

Its playing for me. What's the issue?

 

great!

 

I had problems with my computer getting and then playing

and even now I sometimes get a dialog box and have to retry the download.

 

so I am wondering how accessible

 

the PerimeterInst. has a whole bunch of recorded video of talks by Roger Penrose etc etc.

 

but also the issue is Bilson-Thompson. I think he has a good idea that just might work and simplify both the std. mdl. and quantum gravity.

[guardian]

Took slightly longer for me to get going since I had to d/load some sort of a decoder. Watched 13 mins. but cannot watch the rest yet. Although more appealing as a visual presentation I get a feeling it'll be a rehash of the paper (apart from the background - ie prior versions of preon model), am I right? I understand the paper completely. Are there things in the presentation (again bar the background) that are not covered in the paper?

[Martin]

atlantic and ecoli you both sound like you understand the problem of explaining space or spacetime using material metaphors.

 

heh heh, the catch is there arent AFAIK any surefire material metaphors.

 

we are all more or less equally bad at explaining the bigbang to bascule

 

there is a lot of explaining work at SFN and maybe I am just trying to entice you to do more of it

actually ecoli I think you already volunteer quite a bit, I think I remember your doing that

 

that said, there is the Bilson-Thompson business.

 

It would be so great if B-T really has uncovered some underlying structure in the Standard Model

 

his braided strands (representing particles) can serve as the ties in a network---and such a network could represent a quantum state both of matter and space.

 

several approaches to quantum gravity use something like a network to represent a state of the (gravitational field or) geometry of space.

 

Sundance B-T was in Canada for a while working with Smolin, on this kind of combination of loop quantum gravity with a theory of matter. they will almost certainly co-author a paper---one should appear, as a wild guess, in about 6 months.

[Martin]

... I understand the paper completely. Are there things in the presentation (again bar the background) that are not covered in the paper?

 

guardian thank you. I am glad some others like yourself have checked this out.

Yes there is some new stuff towards the end that is not covered in the paper.

 

But it is extremely tentative. to the extent that his talk is about solid stuff it is all in the paper.

but even so the talk is helpful. he gets asked questions and is forced to think and react. one gets a sense of what he feels more sure about and what less sure

 

then at the end he talks a little about work he has started with Smolin on merging his stuff with the spin networks of quantum gravity.

(that may actually help him complete his treatment of matter because the gravitational field could supply the equivalent of a higgs mechanism and gravitons, so that he does not have to worry about producing these things out of preons.)

[Royston]

That's all I know...so far' date=' an infinite universe has no need to start again by exploding into another infinite, because it is infinite...is that right ? Feel free to rip this apart, I'm under the weather today so not thinking to clearly. .[/quote'] Yeargh, obviously had mucus on the brain as well as up my nose.

 

I think this is one of those 'what if' questions though' date=' which (probably eat my words now) that I'm not sure anybody can answer.[/quote']

 

Well I'm currently printing my post, and will lightly season it with some sea salt and crushed pepper corns.

 

I've been thinking a lot about what Guardian has posted though, and there seems to be a link between CP symmetry violation and the inflation period between the stage of a unified force to the temperature changes that caused the seperation to the forces we know today.

 

If a repelling insufflation force was generated through a breaking of the unified force...dark energy, and as time went on, radiation was generated through annihilation of quarks and anti-quarks to re-instate the electroweak and nuclear forces. Is there the possibilty that between these two periods that dark energy interacted and isolated electrons from their annihilation when it was a more dominant force (which it would of have to been at some point to cause inflation), by acting like the electromagnetic force but repelling...leaving an electron to roam free ?

[phcatlantis]

1. I agree that the universe looks spatially flat' date=' if you look at a large enough piece of it. Or else ALMOST flat. Astronomers have this number Omega that they measure and they get values like 1.01 +/- 0.01.

If Omega = 1 exactly then the U is spatially flat. Which contains the idea of infinite as the most likely (but not the only possible) realization.

But if, say, Omega = 1.01, then the U has to be FINITE with a slight curvature. and we dont know which it is----exactly 1 or just a bit over.[/quote']

 

Just wanted to add something to this, make sure its absolutely clear.

 

The reason why cosmologists can talk about the extent of the universe based entirely on that value, omega, is because the field assumes the cosmological principle: the universe is homogenous and isotropic on a large scale. That's to say that if we measure the large scale curvature at any place in the universe, if this principle holds we should get the same value for Omega. The best way to think about this is consider some the outer skin of some geometry that yields all positive or zero values for curvature but is not closed (say a cone with a rounded tip and a base extending out to infinity). Sure, its infinite, but omega would not be the same around the tip as it would be along the surface extending to the base. On the other hand, its pretty easy to see that a sphere or some other geometry with the necessary characteristics, has the same average intrinsic curvature everywhere.

 

2. space doesn't need some surrounding space to expand INTO

space simply expands.

 

I think in this case its useful, and slightly less misleading, to actually think about content (say a volume of dust or an area of specks) rather than space. The rubber sheet analogy captures the idea that we can see content receding in expansion, but at the cost of leaving laymen with the impression that content is just lying on some material thing that is pushing it apart. If you...

 

1) think about content growing increasingly diffuse or concentrated due to some interaction with itself, as you would with a volume of gas or dust in your everyday spatial experience.

 

2) then observe that the idea of distance between points in that content changes with the distribution of that content

 

...then I think that pretty much captures how general relativity, describing the behavior of geometry and topology due to some distribution of mass-energy, and astronomy, which characterizes that distribution empirically, knock boots to give us an extremely elegant cosmological model.

 

I think a better analogy would fall along these lines, getting away from a material notion of space and space-time and getting people to think about dust clouds. But I'm quite sure somebody else can explain it better than I can

[Martin]

thanks atlantis, helpful clarification.

[guardian]

Martin, one other thing that has left the preon model incomplete - angular momentum? Or did I miss something...hmmm

 

Still haven't watched the presentation in its entirety but I AM interested in the Q-A section.

 

Oh, and another thing. Although it says it has solved the asymmetry problem - the asymmetry persists! We still have dominance of matter.