# Thread: Eleven Dimensions in String Theory

1. ## Eleven Dimensions in String Theory

Is this mainstream?

The theory of eleven dimensions (11D) actually was first postulated nearly 60 years ago using the Standard Model. ( http://en.wikipedia.org/wiki/Standard_Model ) It sat there as a possibility until it was pushed into prominence with String over 20 years ago when String ideas started to prove themselves as the only possible way of expanding the Standard Model to encompass everything. Since the 11 D Standard matched 11 D String this has become the key for advanced theories during the last 20 years. So we are referring to an idea that is half a century old and has survived decades of scientific debate and has only gotten stronger support. The Wired article has been based on incomplete data. This is common with popular journalism. Even journalists in technical magazines don't have the required background to have followed fully the debate.

The idea that main stream science doesn't consider String strong enough is invalid. Everyone of the top theoretical physicists in the world use String. Hawking is not alone in his use of the theory.

Here is how we get the 11 plus dimensions. Consider a shadow on the ground. You don't have to look at the object making the shadow to calculate its size and shape because you know how light is projected and the angles that the light has traveled. So from a two dimensional object you can calculate what the three dimensional object looks like that projected the 2D shadow (you can take this up to 3D shadow and 4D object if you measure over time). Doing the same type of measurements on our 4 D universe you can calculate that 11 Ds or more project themselves onto our 4 D universe by the way those shadows caused by the 11D make themselves felt on our 4D.

Both the General theory and String come up with at least 11-dimensions. Since the 11-D General theory was developed in the 1950s this is a relatively old physics concept. There are just enough gaps in the real world that require more than 4-D to get the mathematics explaining them to work.

Consider this: You have a shadow moving on the 2-D ground. You use mathematics to explain how it moves and distorts during the day. The math becomes very complicated. Now instead of using the 2-D math you create a 4-D world where there is a stationary tree that doesn't change directions or size and project a shadow onto the ground as a light source (sun) moves. The math is much easier and you have rendered the 4-D world into a 3-D event (motion across a 2-D ground with time the third dimension). This is what is happening with the 11-D universe and our 4-D ability to see it. The math tells us that there is a projection from more dimensions into our 4-D shadow world. We are now in the realm of CSI. We get clues about the crime, or in this case the way the universe works. We then build up what has to happen for these events to occur. Blood on the ground means that someone was bleeding. Typing the blood tells us about the person or persons who bled. We have never and can not physically see the event but the clues tell us that it happened. We can not see the 11-D but the physical clues tell us that they are there.

M-Theory is not a theory in the mold that most people think of. It does little to explain a specific physical event. It is a framework that explains how the math describing something such as Quarks and the math explaining something such as a super nova relate to each other and how to pull the overlap between the two extremely different events together. It sets the parameters on how these different equations have to be framed so there can be a passing of information between the completely different events. M-theory is a theory that sets the conditions that all of the other, more specific, theories have to meet.

2. Yep .. 11 dimensions String and M-Theory gets my vote.

Mainstream 'Mathematical Theoretical Physics'.

(Not so keen about the rest, though).

Regards
Last edited by Selfsim; 2012-Mar-05 at 02:22 AM. Reason: Added qualifiers

3. I've heard (and this is completely unverified) that 1 time, 3 real and 3 complex make 10.

4. Where is that quote from?

Is it mainstream? It's closer to mainstream than a lot of wild ideas, and the math works out (or so I'm told). The problem (as I understand it) with string theory is that there are still a few competing approaches to it, and none of them have been tested experimentally. Mainly because nobody can come up with an experiment to test the predictions. The energy requirements are beyond current technology, or something like that.

Fred

5. Originally Posted by Nowhere Man
The problem (as I understand it) with string theory is that there are still a few competing approaches to it, and none of them have been tested experimentally. Mainly because nobody can come up with an experiment to test the predictions. The energy requirements are beyond current technology, or something like that.

Fred
Not quite … see here … String Theory Test Progress.

So much emphasis is commonly placed on the test difficulty issues .. and yet I rarely see anyone attempting to explain why M-Theory manages to explain super condensed physics behaviours and the fundamental particles.

Rather than spend this thread poking at the well-known gaps, why not have more explanations for why it manages to hang together so consistently, when it could easily fall apart for any number of reasons ?

Its overall high degree of self-consistency is the more perplexing and interesting issue, as far as I'm concerned … and it is almost always avoided for some reason ... why is that ?

Regards

6. Originally Posted by Roobydo
1 time, 3 real and 3 complex make 10.
So do dimensions multiply with each other when there are more than four?
Originally Posted by Nowhere Man
Where is that quote from?

Is it mainstream? It's closer to mainstream than a lot of wild ideas, and the math works out (or so I'm told). The problem (as I understand it) with string theory is that there are still a few competing approaches to it, and none of them have been tested experimentally. Mainly because nobody can come up with an experiment to test the predictions. The energy requirements are beyond current technology, or something like that.

Fred
Thanks - the quote is from a collection of posts here in a discussion of Stephen Hawking's book The Grand Design. I lack the knowledge of physics to assess it, and find the idea of more than four dimensions impossible to imagine.

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So much emphasis is commonly placed on the test difficulty issues .. and yet I rarely see anyone attempting to explain why M-Theory manages to explain super condensed physics behaviours and the fundamental particles.
Except it doesn't really explain the fundamental particles - it just makes their properties depend on the configuration of the Calabi-Yau manifold which is not that much better than just plugging some numbers in. And posits that they are 'made up from' a more fundamental object that can have several configurations. I'm more of a fan of how it offers a means to explain why 3+1 dimensions are what we see.

String theory is a nice idea. It may even be right. Far too early to say. The linked thread seems to have almost no actual tests for it. One speculative cosmological model, one attempt to link it to quantum information theory and a few other hints. It is not the only contender for the next standard model, it is one of a few. So long as that is never forgotten (a few of the more evangelical string theorists seem to forget that, intoxicated by its mathematical depth I guess) it is a valuable piece of the speculative physics mainstream.

8. I shall remain sceptical... I claim to understand infinity. A concept I grasp.

I also claim to understand a three dimensional space concept with a addendum of time as a locater in time space..

I have failed to establish a need for any other dimensional concept.. Is it MAINSTREAM.. No it's not.

As any explanation I might except as mainstream would need to be of science and testable.. and to be honest.

Those that pro-port a many dimension reality are a small group of self appointed experts talking to themselves..

and amongst themselves.. I am NOT included and might be quite wrong. However...

I would not be alone in thinking science fiction can be found as true, or not.

To lift this eleven dimension proposal from fiction to fact simply requires a explanation..

When I see that explanation I will judge it., and still waiting.... The Emperor is naked.

9. Eh. It may not be "mainstream" but it is an interesting study of how mainstream scientists brainstorm and evaluate new ideas.

Many of the documentaries about string theory are a who's who scientists getting camera time; what they lack in detail (ok, sometimes they just laugh at questions) is made up for in publicising science in general.

The subject reminds me of the "What if our star had a Nemesis companion that rained comets down on Earth?" semi-serious theory. While not likely or perhaps completely impossible with the 'scopes and surveys we have today, it is a fun experiment because the limits are easy to describe the effects are immediately important.

10. Originally Posted by Robert Tulip
Is this mainstream?
I don't think much of that article exerpt, wherever it's from. It leaves out so much. Superstrings is a developing theory. There were two superstring revolutions, which, well, revolutionized the investigation over the last several decades. In 10 dimensions, there were five viable string theories. Witten added one dimension in order to unify the five, but that wasn't 60 years ago. It was Kaluza and Klein and Gunnar Nordstrom who first tried the idea of adding dimensions in an attempt to unify existing theories, and that was 90-100 years ago, and they only went to 5D. I don't know what 11D theory the article is referencing from 60 years ago, and the article doesn't say. But the number of extra dimensions is not just ad hoc.

Fortunately, string theory doesn't go about things in such an ad hoc fashion, picking an arbitrary number of dimensions, scaling up the size of the matrix or Riemann metric tensor, and seeing what forces you can or cannot accommodate. Instead, the theory tells you exactly how many dimensions are needed for the job, and that number is ten – the four dimensions of the “conventional “ spacetime we probe with our telescopes, plus six extra dimensions. -- Shing-Tung Yau

I don't know how "mainstream" is defined, but string theory remains speculative. Speculative or not, the investigation has led to the solution of long-standing problems and conjectures in mathematics, so it has been productive. Some physicists say string theory is so beautiful and perfect, it must be right. And it may be, but we're not there yet. We were looking for a theory that explains our universe and why it is the way it is, with the physical constants the way they are, etc. Yau proved that 6D Calabi-Yau manifolds exist, mathematically, and some years later physicists decided Calabi-Yaus were just what string theory needed for the compactified dimensions. A lot of work has been done with this framework, but it's not really a given. Some investigators are looking into non-Kahler manifolds (Calabi-Yaus are Kahler). The unexpected result is that strings and Calabi-Yau lead us to the conclusion that there must be somewhere on the order of 10500 viable solutions. That's a far cry from the single one we were looking for that explained our universe. Some physicists have taken this result and proposed highly controversial conclusions.

We happen to be living in a time when theory has gone far ahead of observation.

11. Originally Posted by Cougar
We happen to be living in a time when theory has gone far ahead of observation.
What, no comment on my bold assertion? Well, I'll add that we are probably also living in a time that has the most scientific observations being made, by far, than at any other time in human history. There's practically too much data!

12. Originally Posted by Cougar
Originally Posted by Cougar
We happen to be living in a time when theory has gone far ahead of observation.
What, no comment on my bold assertion? Well, I'll add that we are probably also living in a time that has the most scientific observations being made, by far, than at any other time in human history. There's practically too much data!
Can't let this (or your last post#10) go past without comment Cougar ... (thanks for both of them. ).

I get the firm feeling that we're heading towards a time where models will supersede, (or more like .. consume), traditional science 'Theory'. The mathematics in String Theory, (ST), for example, seems too complicated for most humans to manage and keep track of, so I might have a guess and say that somewhere, somehow, a computing solution will be developed to overcome our shortcomings in this area. (If it hasn't already).

The behaviour of collective humans is already being directly influenced by extraordinarily complex climate and economic models, (and the seemingly obligatory, accompanying system crashes and their impacts (eg: the apparently unavoidable stock exchange crashes, of recent times)).

I'm unsure whether the traditional philosophically based methods of distinguishing speculation, from theory, will continue to have quite the same meaning in the brave new 'modelled universes', created on our behalf, within these modelling environments (??). Does anyone really have a grasp of the full impact ST's 'extra dimensions' on our understanding of Astrophysical phenomena ..?.. and are we destined to have to blindly accept the output of some algorithm so complex, no human will ever really be able to evaluate its true physical authenticity/appropriateness ?

The curious thing would seem to be that the data you mention, also seems well suited to exactly the same computing environments … when this data comes together with humanly incomprehensible modelling algorithms, whose output then is used to synthesise other models, do we also ultimately lose track of physical reality ?

Regards

"No human will ever really be able to evaluate its true physical authenticity..." I claim to.

It's very easy. It's rubbish.

It seems to me that a minority attempt to stamp their concepts of reality upon the rest of us.

I repeat. It's rubbish. All I ask is 'show me ?' Be brave. Step forward. Speak clearly..

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You understand String Theory as well as Witten and co then? You are welcome to believe that you have the authority and knowledge to dismiss it like that but I am not sure I believe you do. I may not like it all that much but I respect the minds behind it and would be very, very loath to just write it all off as rubbish.

15. Yes 'Shaula' that would be my view.. I make assumptions of clarity. Uncomplicated and true.. No hidden agendas.

Yes, that is why I have now asked a separate question.. That I do at this point dismiss it all as nonsense.

and yes... I have read much of this subject., and in reading so much have not gained clarity..

Respect for the collective minds of many, I do doubt my resolve.. I find myself in a quandary.

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So, argument by incredulity.

As long as you accept that your attitude to the theory is unscientific and based on your personal beliefs (and hence not one you should try to foist onto others) then that is all fine. I try to keep my personal beliefs out of any assessment I make of String theory when asked a question. I can point to weaknesses it has and to strengths. But I would never dismiss it as nonsense without understanding it.

17. Originally Posted by Robert Tulip
So do dimensions multiply with each other when there are more than four?
I don't think he's multiplying the 3 Real times the three Complex to get nine, probably just means that the complex ones have two dimensions each, the real and the imaginary.

Thanks - the quote is from a collection of posts here in a discussion of Stephen Hawking's book The Grand Design. I lack the knowledge of physics to assess it, and find the idea of more than four dimensions impossible to imagine.
It's from three separate posts, all by the poster WONK. The first two paragraphs are the last post to the thread (Sun Mar 04, 2012 5:41 pm), the third paragraph is from the middle of a post (Sat Mar 03, 2012 11:08 pm) and is the part you responded to. Last three paragraphs come his 4th post to that thread (Thu Nov 25, 2010 11:56 am).

18. Originally Posted by astromark

"No human will ever really be able to evaluate its true physical authenticity..." I claim to.
Mark;
Could you please discuss the options for parity assignments in (on-shell) N = 2 five-dimensional Yang-Mills- Einstein supergravity theories (YMESGTs) coupled to tensor and hypermultiplets on the orbifold spacetime M4 x S1/Z2 for us ?

Many thanks,
Regards

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Originally Posted by Roobydo
I've heard (and this is completely unverified) that 1 time, 3 real and 3 complex make 10.
Unless time is a complex value, which SR predicts when velocity is superluminal. I really don't know anything about string theory, but if 11 dimensions helps to better explain the four dimensions that I'm familiar with, then I'll believe it, although I would be forced to defer to the "experts" in telling me that the math is indeed correct. I'll be very supportive if it helps to do away with dark energy and dark matter (which I suspect are the modern day equivalent of epicycles; they help theory match the observations, but are fundamentally a theoretical dead end).

20. Originally Posted by jfribrg
I'll be very supportive if it helps to do away with dark energy and dark matter (which I suspect are the modern day equivalent of epicycles; they help theory match the observations, but are fundamentally a theoretical dead end).
Well, epicycles had a very specific rationale and procedure for explaining (and predicting) the observations. With dark matter, we have no specific understanding of what it is or how it works. In this case, the theory of strings may come to the rescue. All the particles and bosons have "superpartners" in string theory. One or more of the superpartners may turn out to be the dark matter we've been looking for. But as of yet, no superpartner has ever been detected. With ongoing operations at CERN, this may change in the not-too-distant future. Or it may not. When one doesn't know one way or the other, pronouncing it rubbish is premature.

21. Astromark, do you believe black holes to be nonsense? They first existed only in the minds of theoretical physicists. They still have not been directly observed. They are considered real by inference; by observing the speed of stars orbiting close to them and other factors.

You must believe atoms exist as we can now directly observe them but they too once existed only in the minds of theoretical physicists. How about electrons? We still haven't directly observed them. Are they nonsense? No, because the model we use for practical electronics, etc. employs them, but they once were considered nonsense by many people.

Please Mark, get over this notion that if you can't directly see, smell, hear, taste or touch something, to discuss its possibility is utter nonsense.

I think your frustration is primarily caused by knowing that you cannot discuss many theoretical models because you would have to invest much time and learning to get up to speed on them. I'm in the same boat, but so what. I can't understand doctors discussing theoretical operating techniques for the future or chemists discussing properties of a theoretical new compound, so should I write off what they're discussing as nonsense? Of course not.

New discoveries are often born in theoretical models -- please don't try to stifle them unless they are being prematurely proposed as fact.

Mike

22. Originally Posted by Robert Tulip
So do dimensions multiply with each other when there are more than four?
No, each complex dimension is the same as 2 real dimensions.

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Originally Posted by Robert Tulip
Is this mainstream?
Unfortunately yes... but... keep in mind there are some people out there who thinks four dimensions is plentiful and evoking 11 is superfluous and pretty much ridiculous.

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