If we only perceive the universe as 4 dimensional, when it is actually 2-dimensional, then is it a stupidly naive question to ask why we perceive in 4d, and not in 2d? And how is it that our senses deceive us in such a vile manner?

my notes, so far, ...

Prof. Susskind describes a model with the initial condition of a spherically symmetrical shell of matter undergoing collapse towards its centre. Newton says that such an object exerts no net gravitational influence on a test particle inside the shell.

The collapse reaches rcrit below which light cones point inwards.

should i go on... ?

Please do, i'll grab a chair.

Well... and here I'm open to correction...

This model, henceto_under_therefore, predicts a shell of matter + 1 other scalar field around you, the observer inside the shell. So, what do we see? CMBR from a prior plasma state + Higgs. Hey prongo! An idea that seems to work.

(tiling spheres with squares gets a bit trickier near the poles, in my experience...)

So, this projection, it is beamed from the eyes of a god/dess or a cthonic being on to a scared child's bedsheet or sumfink?

No, you are here on earth inside the very dense sphere of stuff that you see from earth as the CMBR. It's what you see with photons in your eyes.

We see the projection of the shell (the "hologram", "the piece of film") in the CMBR.

ETA The object is a model, 1 can hold it and see it from the "outside". Perhaps this is where i get the words wrong?

This is where we all need to take a deep breathe and say "Shut the fuck up and calculate"

If we meander away from the actual physics of it, we will soon end up talking about sky-daddy

Finally finished watching the video. Great video. I didn't get why the guy sitting next to Susskind hoped to find a deterministic world living inside the sub-Planck level. What would that achieve, or explain?

This World Science Festival really seems to have been a not-to-be-missed extraordinary event. There are some exceedingly interesting discussions between the world's leading Physicists, in every field of Physics. Here are some eminent Physicists including Alan Guth, Andreas Albrecht and Neil Turok talking about the multiverse:

bookmarked

wot? no twistors? gr8 vid.

Good thread. I should point out that, although String Theory isn't currently testable, it is currently falsifiable, in the search for Supersymmetry. String Theory relies on SuSY, so if SuSY is falsified, String Theory falls with it.

Oh, and that Sherlock Holmes quotation is one of my pet peeves, not least because it's nonsense. Meretricious nonsense, but nonsense nonetheless.

Well, that was an excellent discussion, although the key take-away for me was that cosmology in general is in a pretty bad shape right now. Turok's assertion in the beginning that the participants agreed with each other more than they disagreed didn't seem to bear out over the rest of the discussion. I was expecting a fist-fight at some point, although I understood where each of them was coming from.

I agree with Guth that the Turok-Steinhardt Cyclic universe doesn't achieve much beyond a somewhat contrived workaround for the big-bang singularity. We still have to deal with all the other divergent infinities that are entailed by multiverse models. I agree with Turok that we need models that make testable predictions (which Guth's inflation/ pocket universe model is not), but not with his assertion that his Cyclic Universe is such a model (blue shifts in undetectable gravitational waves, seriously?). Also, reality has no requirement to be testable by humans, so there is no guarantee that testable models will improve our understanding of the Universe. Albrecht seemed to hint at a possible resolution that has something to do with a finite, holographic universe, although he didn't elaborate on the idea. My own instinct is most closely aligned with that of Albrecht, but I'm no professional physicist, so what do I know?

hackenslash wrote:Good thread. I should point out that, although String Theory isn't currently testable, it is currently falsifiable, in the search for Supersymmetry. String Theory relies on SuSY, so if SuSY is falsified, String Theory falls with it.

True, but if Supersymmetry is conclusively shown not to exist, then String theory won't be the only victim. We will be back to the drawing board with much of modern physics.

The topic seems to have wandered into debating cosmological models to seek out their logical inconsistencies (if any). Obviously, more, and less-uncertain, data points are required to help eliminate a few more (models). The upgraded LHC cannot turn on again quick enough.

newolder wrote:The upgraded LHC cannot turn on again quick enough.

Cheers to that, and let's hope they can confirm SUSY this time.

iamthereforeithink wrote:

newolder wrote:The upgraded LHC cannot turn on again quick enough.

Cheers to that, and let's hope they can confirm SUSY this time.

hmmm, there are more ways to get more stuff than supersymmetry alone. Andrew Kels' recent solution for the Star Triangle relation gives a clue that Ising (lattice) models might help...

There's an evil little part of me that wants SUSY to be falsified.

hackenslash wrote:There's an evil little part of me that wants SUSY to be falsified.

Doesn't the recent finding that electrons are perfectly spherical as far as we can measure contradict super symmetry?

I was asked to post in this thread by someone I know IRL, not sure what they want me to say but the answer to the question immediately above is no. By "electrons are perfectly spherical" I assume you refer to the recent improvement in the limit on electron dipole moments, here: http://arxiv.org/abs/1310.7534. In Supersymmetry one can predict a large effect there, but this depends on the parameters. In particular it depends on large CP violating phases in the parameters. Since no electron dipole moment has been observed most people working on SUSY assume some mechanism forbids these phases, and nice examples of such mechanisms have been proposed. The latest measurement simply strengthens this conclusion. The measurement is important as it increases limits on these parameters and is complementary to LHC results but the significance seems to get massively exaggerated. If you want a better idea of what parameters are restricted by this measurement you could read:
http://inspirehep.net/record/1256085