GRAVITY PROBLEMS -- off topic from {Falsifying a young Universe}

Well of course it is.
I never denied that.However, from observational evidence, it is much more reasonable that Dark Matter is the answer rather than a modification or replacement of General Relativity.
That's what I've being saying.

????? What do you mean by an insignificant time difference? The problem is that General Relativity is too mathematical in character to be expressed in English and it's limits aren't related to its explanation of gravity above the Planck level. Hmm.
Thats all I'll say.
If it's true, then every physics department in the country should have one of you.Again, similar to simple, your comments actually make no sense in relation to what theoretical physics is about.
It's like your arguing against a persona you've constructed yourself.

I understand what every word in this means, but how does it really relate to the limits of General Relativity.
You've just quoted a page on LQG thinking it relates to what I said."There's a lot we don't know about nothing"
That is certainly true, but how does it relate to the limits of GR above the Planck level. That's equivilant to saying:
"This wire has a Voltage 0.05 volts more intense than this wire.
What a boring fact, therefore all of electronics is boring."Just because a single case example is monotonous doesn't mean the theory hasn't interesting intellectual depth.The fact that somebody who is a meter above me has a clock that ticks almost infinitesimally faster than mine, isn't that interesting to me either.
However General Relativity is one of the greatest works of human thought I've ever encountered. They're all a hundred years old, hardly "de jour".
Besides, that's all fine and well, but what we know is immense.
I don't know how much we know amounts to, compared with all there is to know, however we still know a hell of a lot.
You can point out that there is something beyond what we know, but so what?
Of course there is something beyond what we know, of course we might not be able to understand it.However look into what we know and you'll see how much we've accomplished.
General Relativity and Quantum Field Theory, tell us things about the world we couldn't have ever made up in our strangest fictions and to dismiss that knowledge because it is limited makes no sense to me.This message has been edited by Son Goku, 10-16-2005 07:49 AMThis message has been edited by Son Goku, 10-16-2005 07:51 AM

RAZD, if I can remember where I saw it, I'll get you a link where General Relativists and Cosmologists have come up with an idea that a large chunk of the galaxy rotation anomaly comes not from Dark Matter, but from the fact that we are using the Post-Newtonian approximation, rather than proper non-perturbative General Relativity.So although the correct field equation is: When we are trying to model systems in GR, this proper equation is far to difficult to use as it is non-linear, so we use its linear approximation: However the Linear approximation could be correct at the Solar System level, but incorrect at the galactic level.This message has been edited by Son Goku, 10-16-2005 10:43 AM

What has that got to do with what he said.
He wasn't talking about what is right, he was refering to the fact that anything you quote from John Baez or others, isn't going to suprise him or be a mental bombshell, because it used to be his job to read that stuff. This paragraph strongly indicates that you don't understand how theoretical physics operates.
You are refering to specific intial conditions problems rather than a theory problem. "Time is the direction in which Stress-Enrgy must be extended due to the geometry of Lorentzian manifolds."
There is the actual answer from General Reltivity.This message has been edited by Son Goku, 10-16-2005 03:59 PMThis message has been edited by Son Goku, 10-16-2005 04:07 PM

Mathematics can't just say what you want with complete freedom, especially in physics.

Actually they do agree.
It is possible to construct a Quantum Field Theory on a Curved background and it is possible to generate a classical spacetime from a Quantum Mechancial Stress-Energy Tensor.It is not a case that they don't agree.

It is simply that General Relativity doesn't quantize.This isn't truly a conflict, the two can still be used together.
It's just a case that you have to get conditions from one and then use the other.The whole "General Relativity and Quantum Field Theory" issue is simply that they aren't one single conceptual entity.This message has been edited by Son Goku, 10-21-2005 02:05 PM

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It does in d=2

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Is that just the Turaev-Viro model in Loop Quantum Gravity or is standard QFT able to do it when d=2 as well?

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And it should be pointed out that "quantize" means to take a classical theory and use it to extrapolate the quantum theory. It does not mean that there is not a quantum theory of gravity, just that our usual prescriptive (and rather crude) methods of getting a quantum theory from a classical theory do not work.

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Would your personal opinion be that we need a new method of quantization or do we just need to start at the quantum level?

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Topological field theory is an awesome subject...
But I'm going to bed, so if you want to talk more about it you'll have to wait

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Cool, thanks.
I actually have a one or two things to ask, but I'll wait till tomorrow.

Right, my questions are, if you have the time to answer:1)Your personal opinion of String Theory and Loop Quantum Gravity?2)Do you believe we should put more attention into trying to find the electronuclear/G.U.T. force?3)Opinions on how we'll do in the next few years when it comes to finding exact solutions of GR and QCD?

It's very kind of you to take the time at all, so thanks very much. I see what you mean. I suppose the Field Equation says that itself in a way. "Why Lagrangian Mechanics works?"
That has given me a lot of food for thought, thank you.
I'd gotten a bit too used to just thinking of the Lagrangian as a tool. The plight of Numerical Relativity. I'm a little bit of a phenomonology guy, so I like it when "wierd" things turn up in certain solutions, like Closed Timelike Curves, e.t.c.
However you're probably right in that it won't help with post-Standard Model physics.

You see, this is what always "screws with your head" when you're talking about General Relativity.
You can think about and discuss static 4-D geometry very easily (once you've broken the conceptual barriers obviously) yet your "thinking" and "discussing" are dynamic 3-D processes.
I'll often explain the whole thing of the Universe as a static 4-D Lorentzian surface to somebody and while explaining it realise, that while it is true for large scale structures, me and the person I'm talking to are definitely 3-D and time evolved.In short big things are more comfortable with (4), smaller things with (3+1).I brought this up with a few philosophers I know and they were shocked that physics contained such an interesting idea.

You stand a great chance of success.
I've a few friends in engineering who have learned general relativity. You definitely have enough of background to start on General Relativity.
The perfect book for your level would be Bernard F. Schutz "A First Course in General Relativity"
Here is what it looks likeIn my opinion, General Relativity is lot easier to learn than Quantum Mechanics, because it's self-contained and doesn't require a broad knowledge base already.All you need is calculus and a knowledge of special relativity, which Schutz will go over any way.If you have any questions at all feel free to ask.

This is perhaps the most important piece of advice.
My second choice would be D'Inverno, in fact Schutz and D'Inverno were the books I learned it from.
My praise for Schutz is mainly for Chapter three (one of the best intros to Tensors I have ever seen) and its excellent exercises.Whatever you do have two texts for GR.And if you ever do QM at least three.Anyway, in my opinion Schutz and D'Inverno are the best places to learn GR.For intermediate General Relativty, after you're done with the basics, I think Wald is best for Mathematics and Carroll for intuition and Black Holes. I never read Stewart's Advanced General Relativity, in fact I've only ever skimmed his Elementary General Relativity.As for Felice and Clark I thought it was like the end of Wheeler Misner and Thorne, except more serious and little more fully developed mathematically.
For instance the Spinor and NP sections were a good read in MTW, but you learned more in F&C.(As a side note: Although not that Mathematical, I thought Landau and Lifshitz: "Classical theory of Fields" has one of the best intros to the BKL map.)