Missing Matter

This is by far the key point, and why I would find such a discovery to be one of the greatest of the past fifty years or so.

Great way of putting this Never's a bit too strong, don't you think? We eek out quark-like behaviour with our deep inelastic scattering, after all.

Yep We tend to discover new particles by their distinct decay processes - i.e. what we actually "see" are the decay products, and their characteristics are used to infer the characteristics of the parent particle. Stable particles don't decay much for obvious reasons But they can be revealed by the *missing* characteristics following a collision. Unfortunately, this is also how we can detect for extra dimensions, so it's not an easy task differentiating all of these possibilities. But with some good luck it can be done... See SG's earlier post.Edited by cavediver, : No reason given.

Heh, heh - I've just noticed the name of the guy who started this thread. Shall we offer a prize to the first EvC'er who can explain why that name is particularly appropriate to a thread on WIMPs? but first you have to see what I'm getting at

Show off

The simple answer is that when you formulate string theory in d space-time dimensions, you obtain an anomaly which destroys the physical characteristics of the theory - however the anomaly contains a factor of (d-10), so when d=10, the anomaly disappears. This is quite unusal - most physical theories work equally well in any number of dimensions - GR, electromagnetism, etc, and thus they give no clues as to what the dimension of space-time should be. One exception is Supergravity, and interestingly string theory and Supergravity have now revealed themselves as simply different perspectives of the same (M) theory, despite very different origins, and they are the two trheories that actually give important clues to the dimension of space-time.Edited by cavediver, : No reason given.

We can start with a single Lagrangian and go on a long journey of discovery. It will involve many equations and expressions. I'm trying to work out how and it comes back to me why no-matter how many Mickey Mouse undergrad string theory courses are introduced, it is most definitely an advanced post-graduate subject. To understand the fuss and get that 'wow' factor, you really need to be comfortable with Lagrangian formulations of General Relativity and Quantum Field Theory, and have some knowledge of the Renormalisation Group. And this is just the very beginning!!But it is a challenge, so I may well have a go. It may be good to start with an *easy* topic like Hilbert's Lagrangian formulation of General Relativity. How familiar are you with Lagrangian mechanics? Given the fundemental nature of this, it may even be good to start here. This could be a long journey...

I think it depends on what you're trying to explain If we're doing some string theory, then we definitely don't want to be introducing quantum theory this way. And talking about the wavefunction of the field is just destined for confusion, as it now seems that we have two fields!! It is far better to forget all about and just deal with the operator valued quantum field.But the diagrams were nice

I would jut say it is acting on the fock space of states (from a perturbative perspective) Which in turn is just another representation of the operators in the field. In QM, we go from localised point particle (x,p) to infinitely extended and gain lasting impression that there is some reality to . But this is wrong - it is really just a hint that we should actually be using QFT and not QM. And in QFT, "" does not contain any information that is not aready contained in the field - which is why I think it is a confusing and largely redundant notion for explaining quantum field theory. Thoughts?[Of course, if we are working in quantum cosmology and want to emphasise the superspace approach, it is perfect < !--UB -->

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This message is a reply to:
	Message 37 by Son Goku, posted 09-24-2008 7:20 PM		Son Goku has replied

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Replies to this message:
	Message 40 by Son Goku, posted 09-26-2008 8:17 PM		cavediver has replied

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Bringing your comments out of hiding I, for one, was far more inspired by reading stuff way above my comprehension than the toned-down popular accounts - certainly as a child, and even as late as my final year of undergrad, when I was moving into quantum gravity from an astrophsyics background. I'm sure there are some here who will enjoy the jargon... Yep, and my personal view is exactly as you suggest - I view this as backwards, even though it is the obvious chronological approach. I think we get tricked into reading too much into quantum mechanics by taking it before QFT.* I used to debate this for hours with a colleague who thought much as you did - he was very much into the pre-eminence of Hilbert space - or Pontryagin space in his case, as he loved his indefinite norms *ABE: just to be clear - I am not saying that P and Q are primary over the Hilbert Space - in my mind, QM is simply invalid as a description of reality.Edited by cavediver, : No reason given.

No, no, no, no, no... perhaps SG was right and we should have kept this to ourselves. I'm not talking about Quantum Theory being invalid, I simply mean one particular prescription of quantum theory - namely the original non-relativistic quantum mechanics.Quantum Theory is not only valid, it is an essential description of reality...

No, this is merely how some have portrayed the rift, and they are simply confused. And Quantum Theory is deterministic. Some *interpretations* of the quantum/classical transition introduce indeterminism - but it's not in the quantum theory itself.The real barrier to quantising gravity is much more mathematical in nature and is rather mundane to the lay-reader.Edited by cavediver, : No reason given.

No, this is great. I just wish I wasn't so damn busy at the moment - I'll get back to this as soon as I can.ABE Could this simply be a sign that we are dealing with effective fields in 4d rather than the original fields in d-dimensions? Whichever "GUT" (i.e. Sugra, strings, M, etc) we are considering, we are breaking many symmetries to arrive at our target space. Once we lift back up to the unbroken theory, we should regain rep "invariance" - it would be great to make a toy-model of this. Can you provide an example for us to work with?Edited by cavediver, : No reason given.

Gotta say that that's one of the nicest explanations I've seen Though no doubt there's going to be some questions around what you mean by commutative and noncommutative