Can Anyone Explain the Spin Foam Model in Simple Terms?

[Feeble Wonk]

Help. I'm really struggling with the general idea here. The intricacies of the theory are hopelessly beyond my cognitive reach. I'm just trying to get a general handle on the big picture concept.
I read a bit where Lee Smolin referred to this model as a leading theory that characterized space, matter and energy as being emergent properties, while time was a (the?) fundamental parameter.
Can anybody give me a decent (idiots guide) thumbnail version of the theory, and give an opinion as to what the consensus attitude is regarding it within the professional cosmology community?

 

[enorbet]

Since only one response has logged in so far please allow me to at least commiserate and possibly shine an albeit dim light on the subject. While not quite so far removed from experimental evidence as most of the iterations of String Theory, for example, Lee and colleagues are still dealing in predictive mathematics approaching Planck Scale and as much as he valiantly tries to provide valuable insight to we amateurs, I for one find I cannot get very far without struggling with the Math. I imagine this is an obstacle for any responder since the area of any real answers to quantum gravity could conceivably be generations away, possibly many generations.

It helps a little to keep reminding myself this is speculative mathematics and nobody has a truly firm grasp on the outcome. Don't forget that many hypotheses were wiped out by the fairly recent ESA's Integral Gamma Ray Observatory which by extreme good fortune was able to gather substantial evidence that the Universe is not grainy down to 10 Trillion times smaller than Planck Length. This data didn't destroy Spin Foam but it did cause Mr. Smolin to "throw the gauntlet" down to all working on any variation of Quantum Gravity to be especially cautious and to stay on top of new developments.

Bottom line is I suspect it will be a very long time before this subject even approaches intuitive. Some pretty deep Math is a requirement before it even begins to take enough form to approach sensibility. For my part it is a struggle to the point that I can't convey anything concise without merely pointing back to what Smolin has already published. It's like watching a race where nobody knows the nature of the course and whether it is better to be like a dragster or a 4-wheeler... or a tortoise... more a matter of wait and see.

Hopefully someone far more conversant than I can correct or expand on this as it is rather exciting to contemplate.

 

[Feeble Wonk]

Bottom line is I suspect it will be a very long time before this subject even approaches intuitive. Some pretty deep Math is a requirement before it even begins to take enough form to approach sensibility.

Thanks for the effort Enorbet. I was certain the mathematics of the theory would be Greek to me. I was just hoping for a general "intuitive" conceptual description. From what I've gathered, that's not a realistic expectation at this point. I guess I'll have to settle for the basic idea that it's a quantum cosmological theory that utilizes LQG and QFT concepts, and leave it at that.

 

[sandy stone]

many hypotheses were wiped out by the fairly recent ESA's Integral Gamma Ray Observatory which by extreme good fortune was able to gather substantial evidence that the Universe is not grainy down to 10 Trillion times smaller than Planck Length.

Could you elaborate on this please?

 

[enorbet]

@sandy stone - I will try but just know that while I enjoy Lee Smolin and his efforts toward fairly inclusive methods of explanation, I am less well-read from the wide number of competitor/colleagues and find them far more dense and difficult. I barely understood enough to even postulate that the fortuitous gamma ray burst "drag race" would impact more than just the "Holographic Universe" bunch but was interested and a little pleased that Mr Smolin delivered a lecture thankfully available on some video sites even as commonplace as YouTube outlining some of the "direct hits" and collateral damage wreaked by the first solid evidence that the Observable Universe is not grainy down to such an incredibly small scale. I'll attempt to rediscover that talk and link it here in the next day or two to be more specific than I am presently able. I imagine conversing on Quantum Gravity somewhat akin to attempting to talk about the Higgs Field circa 1970 - lots of doubters and detractors and almost no evidence but predictive Math. Thankfully despite many budget cuts all over the world we seem to live in a relative Golden Age of opportunity thanks mostly to rapidly evolving technology.

 

[sandy stone]

Thanks, I was really wondering what accidental observation by a gamma-ray telescope led to the conclusion about non-graininess a bazillion times below the Planck scale. I'll try looking for the YouTube video.

 

[enorbet]

Hello again sandy stone please accept my apology for misunderstanding. You may have found it by now but just in case... here's a simplified overview.

A Gamma Ray Burst occurred as usual very far away/back in time but this time it's onset was luckily noticed. Because the source is not a singularity (perhaps yet) but rather a very large section of Space, measurements could be and were taken of the time each particle took to arrive at our sensors. Had the Universe been grainy, somewhat analogous to the many millions of years it takes photons to reach the surface of our Sun from it's center, it is expected that arrival times over such an unimaginable distance/time would vary wildly. Instead they arrived essentially simultaneously implying no diverting collisions along the way at sub atomic levels. I'm not at all clear as to how this was translated to so far below Planck distance, but that is the conclusion. Here's a decent article among many http://io9.gizmodo.com/5818008/the-universe-probably-isnt-a-giant-hologram-after-all.

 

[sandy stone]

Fascinating! Thank you very much for following up on this point.

 

[enorbet]

Thanks for the effort Enorbet. I was certain the mathematics of the theory would be Greek to me. I was just hoping for a general "intuitive" conceptual description. From what I've gathered, that's not a realistic expectation at this point. I guess I'll have to settle for the basic idea that it's a quantum cosmological theory that utilizes LQG and QFT concepts, and leave it at that.

Although this may be a bit general and definitely a small step, I find this talk "cuts to the chase" and provides at least a glimpse of understanding. Just be sure to use Full Screen so you can read the excellent slides projected on the screen.

Here -