Can someone explain to me the 11 dimensions of string theory

[Sensei]

Not to mention, have you heard of the Hercules-Corona Borealis Great Wall? It looks like the Great Edge of the Great Bubble to me.

 

Interesting

http://en.wikipedia.org/wiki/Hercules%E2%80%93Corona_Borealis_Great_Wall

 

I see one problem with interpretation of it as bubble of other universe - we see it!

If we see photons coming from it, it means speed of light is same as in our universe..

 

In other universe in multiverse theory, speed of light c might (should? because of higher probability) be different than in our own universe.

 

Also astrophysics should perform experiments with neutrinos and other accelerated particles coming from this galaxy cluster to see how different (if different) they are..

It's ten times bigger still, and ten times farther away.

 

 

I see more rational explanation than bubble of other universe - our Universe might be much older than calculated by us currently.

[Schneibster]

You're smart. That's a great question.

 

We only see photons from this side of it. The other side is too far away for us to have ever seen it. Nor will we ever. The universe's expansion has started to accelerate again and it's gone forever.

 

I think it's like champagne that got shook too hard, or a foamy keg of beer. Lots of big empty bubbles and a bit of froth in between them. That bit of froth is the Virgo Supercluster et. alii. Like our galaxy and stuff. That's the shape of the universe. Spit in the ocean. Most of everything is empty.

 

Wow, different alpha or speed of light? Now that sounds speculative. At least anyplace we'll ever be able to see.

 

Folks should keep in mind we can see the most we'll ever see right now. The older the universe gets the more stuff will fall off the edge as the expansion accelerates from the dark energy/cosmological constant.

Edited February 21, 2014 by Schneibster

[Sensei]

Wow, different alpha or speed of light? Now that sounds speculative. At least anyplace we'll ever be able to see.

 

That's not mine speculation!

 

That's whole idea behind multiverse theory.

 

http://en.wikipedia.org/wiki/Multiverse#Level_II:_Universes_with_different_physical_constants

 

Quote

"Different bubbles may experience different spontaneous symmetry breaking resulting in different properties such as different physical constants."

Edited February 21, 2014 by Sensei

[Schneibster]

Oh, yes, on that scale yes very much. That's precisely what I'm talking about. Different Calabi-Yau geometry in the vacuum fluctuation, different value of cosmological constant, different inflation, and etc. on down to different universe. Sure.

 

This is called the "Anthropic Principle." It says, "There's lots of different kinds of universes, we're here because this universe supports ones like us." Is that what you have in mind? I think I might agree with that.

Edited February 21, 2014 by Schneibster

[ajb]

Do you know the Kaluza-Klein theory of electromagnetism?

Yes, of course.

 

There's the first of the seven dimensions of the Calabi-Yau space that defines our universe's particular string theory.

It is true that you can rework the classical theory using principal bundles and end up with pure Yang-Mills, that is we still don't have fermions here.

 

And of course I don't mean to indicate that this most obvious idea is actually a mathematically correct description;

I am not aware of any thing in string theory that singles out the gauge group U(1)xSU(2)xSU(3). The critical dimension itself does not for sure. This is one aspect of the string landscape problem; does (at least) one choice of Calabi-Yau manifold (and choice of fluxes etc) give the standard model and general relativity in the appropriate limits.

 

Even then you should have a reason why this solution is singled out. This is the anthropic problem.

 

Also, please can you explain what you think a Calabi-Yau space is if it doesn't have dimensions?

I think this is to do with the volume going to zero or something similar.

[Alan McDougall]

Like most people in the science community I have a vague understanding of String Theory, but maybe the link below might prove of interest to some members.

 

http://www.damtp.cam.ac.uk/research/gr/public/qg_ss.html

 

Extra dimensions...

One of the most remarkable predictions of String Theory is that space-time has ten dimensions! At first sight, this may be seen as a reason to dismiss the theory altogether, as we obviously have only three dimensions of space and one of time. However, if we assume that six of these dimensions are curled up very tightly, then we may never be aware of their existence. Furthermore, having these so-called compact dimensions is very beneficial if String Theory is to describe a Theory of Everything. The idea is that degrees of freedom like the electric charge of an electron will then arise simply as motion in the extra compact directions! The principle that compact dimensions may lead to unifying theories is not new, but dates from the 1920's, since the theory of Kaluza and Klein. In a sense, String Theory is the ultimate Kaluza-Klein theory.

 

For simplicity, it is usually assumed that the extra dimensions are wrapped up on six circles. For realistic results they are treated as being wrapped up on mathematical elaborations known as Calabi-Yau Manifolds and Orbifolds.

M-theory

Apart from the fact that instead of one there are five different, healthy theories of strings (three superstrings and two heterotic strings) there was another difficulty in studying these theories: we did not have tools to explore the theory over all possible values of the parameters in the theory. Each theory was like a large planet of which we only knew a small island somewhere on the planet. But over the last four years, techniques were developed to explore the theories more thoroughly, in other words, to travel around the seas in each of those planets and find new islands. And only then it was realized that those five string theories are actually islands on the same planet, not different ones! Thus there is an underlying theory of which all string theories are only different aspects. This was called M-theory. The M might stand for Mother of all theories or Mystery, because the planet we call M-theory is still largely unexplored.

[Schneibster]

I am not aware of any thing in string theory that singles out the gauge group U(1)xSU(2)xSU(3). The critical dimension itself does not for sure. This is one aspect of the string landscape problem; does (at least) one choice of Calabi-Yau manifold (and choice of fluxes etc) give the standard model and general relativity in the appropriate limits.

 

Of course not; string theory doesn't single it out. Cosmology does. This knowledge that it must be the Standard Model gauge group, U(1)xSU(2)xSU(3), is empirical. Other universes may have only two, or five or six or more, "large" dimensions, and might have more than one hyperbolic "time" dimension. Unfortunately we don't know enough about M-theory to generate our particular universe from that data. But there is not much doubt on the part of most theorists that there will, eventually, be a particular string theory that correctly describes our physics.

 

 

Even then you should have a reason why this solution is singled out. This is the anthropic problem.

 

It's not singled out; the multiverse/metaverse explores all options. We are here because this is an option we can develop and survive in.

Edited February 21, 2014 by Schneibster

[Implicate Order]

I think we do know what M-theory stands for now. Witten was asked directly at Harvard and his response was that it was up to the interpretation of the user but he actually initially coined it to refer to the term "Membrane".

 

I am getting a bit fed up with the plethora of pop-sci books that have recently come up that talk about the irreconcilable nature of the two most popular approaches (being string theory and loop quantum gravity). It appears to me at least that both theories are fast-tracking towards a unification of approaches as opposed to going in different directions towards mathematical obscurity. The rationale given in these books is that ST and LQG have started from two different commencement points (namely String theory as commencing as a background independent approach from QM whereas LQG commencing as a background dependent approach from GR. ). The assumption is from the pessimists that the gap between the two approaches is getting progressively wider but this is not actually the case. It just takes a good project manager to be familiar with the two approaches to see this in action. No one has bothered to take the time partly due to the fact that the two approaches are mathematically daunting, but also because once again our blinkers come on and we assume that it must be one or the other and not just perhaps two different interpretations of the same thing.

 

String theory has had 2 great revolutions in it's progression that has shifted it's stance towards a fully relational approach and it looks like the 3rd revolution is underway now with the holographic principle. It appears obvious to me that both approaches are now getting onto a similar background dependent solid footing. Namely we have two types of relativistic expression taken from two different frames of reference. That of a frame of reference dealing with a boundary condition (string theories holographic principle) and that of an observers frame of reference dealing with the contents (LQG Causal Dynamic Triangulation). I have already discussed LQG elsewhere so now I will just focus on String Theory.

The folowing information has been derived from discussions and work derived with notable string theorists (Joe Polchinski, Leonard Susskind, Juan Malcadena, Raphael Busso, Ed Witten) and is found in Amanda Geftner's book "Trespassing on Einstein's Law". If we want to talk about a pop-sci book with guts then this is a great read. I site the book as it is important to note that the discussion below is not emanating from my head, but the heads of theoretical physicists who are deeply immersed in the subject.

 

String theory has come a long way since the 90's (Revolution 1) of 10 dimensions where the descriptions were all about vibrating strings and in particular closed strings. Closed strings had much interest due to implications that arose from T-duality and how this feature explained HUP. In T-duality, closed strings receive their energy from two energy forms. Namely vibrational energy (kinetic energy) from the string's vibration and winding energy (potential energy) that arises from the increased PE arising from a closed string winding themselves around tiny curled up compact dimensions of space. When you vary the size of the compact dimension there is a trade off between a strings vibrational energy (KE) and its winding energy (PE). Increase the radial dimension of the space (stretch the spring) and you increase the winding energy and lower the vibrational energy. Increase PE and decrease KE and you get HUP in relation to specifying a strings position or momentum. The smaller the dimension (lower PE and higher KE), the more localised the strings position and the more vibrational energy of the string and the more erratic or uncertain is the momentum and vice versa. What T-duality was showing was the direct relationship between closed strings and space-time geometry. For example assume we have a string in a box (geometric constraint applied to how that string vibrates). In this interpretation we are talking about a 'thing' inside a boundary constraint. If we reduce the size of the box there comes a point when the box gets smaller than the string. T-duality shows that there is another way to look at this interpretation, and that is by removing the energy contents (the string) and talking in terms of the energy of the box provided the box get's bigger to preserve the Law of Conservation of Energy. Now in string theory the energy of the box is referred to as a boundary constraint (sub-manifold) or a 'brane'. This is the first glimpse we get in String Theory of the dynamic nature between space-time and particle properties. It is suggestive that space-time is not fundamental but is simply a different way of looking at the same underlying process - it is a duality. There is a fundamental difference in a theory of point particles and a theory of strings as point particles do not have any winding energy. Strings see geometry differently to point particles.

 

Open strings on the other hand do not have winding energy and they are free to roam through space unimpeded by constraints. Their energy is defined purely from vibrational energy. If you shrink the geometry down to zero it never has an impact on the geometry. What you find is that you can reduce the geometry (described in 9 spatial dimensions and 1T dimension) to 8 spatial and 1T dimension to describe the open string. But how can you have different space-time’s without throwing relativity out in the process? String theorists needed a new way to describe the open string in a closed string geometry.

 

This was achieved by introducing a D-brane to allow for a dynamic geometry and allow for an object (described as an open string) to move in a 9D and 1T geometry. The D-brane was an object in it's own right and you could stack D-branes together. Importantly by allowing D-branes to freely move you could preserve the democracy of reference frames and allow for both open strings and closed strings to exist in the same universe. The duality still remained. What looked like empty space looked from another reference frame as an object (a boundary). For example, what appeared to be background space between strings could also be a vase from another frame of reference. What has been found with D-branes is that the duality of string theory and gauge theory are really the same theory. Both are frame of reference dependent. Both lead to the emergence of classicalism such as particles, fields, forces, the vacuum and space-time geometries. What this is strongly suggesting is that GR and QM are two ways of looking at the same thing but what is changing here is the nature of space-time. As space-time is no longer fundamental, quantum mechanics actually wins the battle. We have an equivalence a the plank boundary between the two theories but below this boundary, we have the quantum domain to deal with if we search further for fundamental causes.

 

Revolution 2 - This kicked off in 1995 when Ed Witten suggested that all the five alternate string theory descriptions of the day were simply different interpretations of the same underlying theory (M-Theory) or Membrane Theory by adding a further dimension to 10D and 1T. This assumption needed D-branes to prove it. In achieving this, Witten needed to turn string theory into a 'local' symmetrical theory rather than a 'global' symmetrical theory and he introduced super-symmetry into the framework. Super-symmetry is the symmetry that allows an observer to shift their reference frame to swap fermions for bosons but in doing so recognising that 'c' ensures this swap cannot occur everywhere at once. Just like gauge symmetry, the misalignment that occurs with phase shift associated with the finite speed of light requires fictitious forces to patch up the differences (and restore the symmetry). Interestingly the 'force' that restores the super-symmetry in this occasion is gravity. It is gravity that restores the mismatched symmetry between inertial and accelerated observers on M-theory.

 

Through this revolution the notion of 'string's' withered away to be replaced with membranes in 10D and 1T yet these membranes are not fundamental in themselves and are reference frame dependent. Strings were important to commence the theory but now with M-theory it was all about membranes. Strings became regarded as simply 'one classical limit'. It is not correct to think of the universe as being made of strings. In fact it is better not to conclude that he universe is made of anything. Each of the 5 different string theories created 5 different sets of particles but what is an elementary particle on one of the versions is composite in another. Thanks to the dualities all 5 theories are equally true.

 

M-theory concludes that there are no basic ingredients. They appear as 'real ingredients' dependent on your perspective. But are there 'branes'? M-theory gets to a point where local objects appear dynamically. The theory is very non-local in nature. It is dependent on the frame of reference of the observer and the notion of boundaries (branes) or stuff inside the boundaries is frame of reference dependent. Now M-theory is starting to be replaced by the Holographic Principle and it appears that the Holographic Principle will be the 3rd great revolution of String theory. On this footing there appears to be significant scope for the merging String Theory and Loop Quantum Gravity camps.

 

Edited February 22, 2014 by Implicate Order

[Schneibster]

I see Einstein as a purely local theory. It's different in other string universes.

 

The string theory that will eventually describe our local physics will conform to Dirac and Einstein theory, among others. It will be degenerate with them in the low energy limit.

Edited February 22, 2014 by Schneibster

[Mike Smith Cosmos]

Holy Cow,

 

I have just read through most of this entire thread ? ( it is the middle of the night to me 4 o'clock in my morning, I just got up for five minutes, thought I would have a peep at the forum , noticed the question on modern theoretical physics about " explain 11 dimensions , had a peep , hooked, wow ! )

 

This whole thing, sounds a very exciting. minefield ! Come gold mine !

 

I need to go and have a drink. Or go back to sleep ! ( and dream myself into one of those Galactic Bubbles , out there in the back of beyond ! )

 

Mike

Edited February 22, 2014 by Mike Smith Cosmos

[Schneibster]

We pretty much know where the universe came from and how it will evolve, and what its large-scale structure is; and we're spit in the ocean just like we always thought, with huge empty bubbles taking up most of space. Our little foamy spitty salient between two huge bubbles is called the "Virgo Supercluster." Ten billion light years thataway, is a huge empty bubble; a few billion thisaway over here is another one, half the size. The edges are called the "Her-CrB Sloan Great Wall" over in the small-bubble direction; the one in the opposite direction hasn't been named yet but takes up a ninth of the sky.

[Mike Smith Cosmos]

last. viewed ,

 

He was last seen , screaming, running down the road in his pyjamas shouting about some mega giant bubble and the Virgo cluster !

 

They locked him up !

 

Can you come and get me out ?

 

Mike

 

 

Ps what is that "great attractor" somebody pointed out to me the other day , doing ?

Edited February 22, 2014 by Mike Smith Cosmos

[Schneibster]

The largest structure of the Universe, defined by Gamma-Ray Bursts

Edited February 22, 2014 by Schneibster

[Mike Smith Cosmos]

The largest structure of the Universe, defined by Gamma-Ray Bursts

Oops! Have we got crossed posts !?

[Schneibster]

Actually I'm still thinking about the Great Attractor but I don't see it as anything but a local phenomenon.

 

 

Maybe we might have a discussion about "local."

[Mike Smith Cosmos]

Actually I'm still thinking about the Great Attractor but I don't see it as anything but a local phenomenon.

 

 

Maybe we might have a discussion about "local."

 

I think this is a link to it

 

http://www.scienceforums.net/uploads/monthly_01_2014/post-98045-0-77505800-1391044308.jpg

Edited February 22, 2014 by Mike Smith Cosmos

[Schneibster]

[Mike Smith Cosmos]

You seem confused . Is the image not coming across ?

 

Repeat link :- http://www.scienceforums.net/uploads/monthly_01_2014/post-98045-0-77505800-1391044308.jpg

 

Mike

Edited February 22, 2014 by Mike Smith Cosmos

[Schneibster]

It still looks local.

[Mike Smith Cosmos]

It still looks local.

Not sure if this is a better link

 

Link. http://www.scienceforums.net/topic/72758-a-lingual-theory-of-everything/?p=789171

 

And next few posts .

 

Sorry ! Had a struggle getting the link copied !

 

Think it is here now. You say , still local ?

 

I think you are right ! It's difficult getting ones head around such vast distances when one is dealing with things up at the foam. Bubble size . ,

 

Mike

Edited February 22, 2014 by Mike Smith Cosmos

[Implicate Order]

The assumption of universal homogeneity and isotropy has always struck me as a controversial assumption. Even WMAP results clearly show anomalies that many conveniently forget to mention such as the Axis of Evil and the Great Void of Erodanus which is indicative of some 'dark flow' and that the universe is not as smooth and featureless as once believed. Still the standard model of Cosmology and inflation lives on. If a theory is to come crashing down, I think the Standard Model is the one to take the hit. There is one big assumption with the Standard Cosmological Model and that is that the universe extends significantly or infinitely beyond the hubble volume as the treatment has always been that the boundary of the observable universe is simply an observational restriction as opposed to a possible 'physical' boundary condition associated with a boundary being inserted in vacuum space.

 

One of the controversial areas from WMAP which is shaking the Standard Cosmological Model and more importantly the inflation model is the 'Low CMB Quadrupole' argument which is the observation from WMAP that there are no temperature fluctuations at scales larger than 60 degrees. This is suggestive that the universe is finite and more importantly puts a limit of the universe to coincide with the hubble volume itself. It certainly does not appear to be a glitch in WMAP data as it is also seen in the COBE data as well.

 

In a De Sitter universe it is possible that the hubble volume actually is a geometric boundary condition like an 'event horizon' of a black hole which, unlike the black hole event horizon is dependent on the frame of reference of an inertial observer from within the universe, as opposed to a black hole horizon which appears to be from the frame of reference of an external accelerating observer of a gravitationally compact object.

 

If this is the case, then we do not need to conjecture what may exist beyond the horizon in classical terms but just recognise that a boundary is, or is not present dependent on the viewpoint of the observer. Namely a 'local phenomenon'. We do not need inflation within the Standard Cosmological Model in this interpretation. The anomalies recorded with WMAP are simply the anomalies to be expected from asymmetrical collapse which is a feature of either environmental decoherence associated with shared frames of reference or singular wavefunction collapse associated from the perspective of a measurement undertaken from a single frame of reference. The notion of 'global' in this context being the universal state agreed on by all frames of reference is an unnecessary viewpoint.

Edited February 22, 2014 by Implicate Order

[ajb]

Unfortunately we don't know enough about M-theory to generate our particular universe from that data.

You are right, in fact it is not at all obvious that M-theory will even contain any solutions that are of cosmological interest.

[Schneibster]

You are right, in fact it is not at all obvious that M-theory will even contain any solutions that are of cosmological interest.

 

Well if there's one of physical interest it will, by definition, be of cosmological interest.

[MigL]

Where did you previously discuss LQG, Implicate Order ? I've been away from this rotten weather for a bit amd probably missed it. I wouldn't mind a read as I'm one of those narrow minded people who prefers it over SString or M-theory and really can't see common ground between the two.

 

I prefer LQG's affinity to GR in having no requirement for a background on which it plays out. Incidentally I would have termed that 'background independant', but I'm not very good at keeping terminology straight.

 

And as been prviously discussed, I detest the fact that SString theory has thousands of possible configurations of the compacted 7D Calabi-Yau manifolds with nothing in the equations or the boundary conditions to point to the right configuration. Having to invoke the Anthropic principle is a cop-out.

There can be no evidence of 'still-born' universes or multiverses other than this one where the conditions are just right for us to exist and ponder these issues.

Other problems include lack of evidence for supersymmetry. Maybe they should call it the God symmetry because it'll probably be harder to find than the God-d**m ( Higg's ) particle. There are also highearchy issues and other problems.

As a previous contributor to this forum used to say, string theory is an elegant theory in search of a universe to describe.

[Schneibster]

Actually, just so you're aware, the reason the term "landscape" started being used is because of the "fitness landscapes" of chaos math applied to evolution in population biology.

 

And the "fitness" of a universe is a measure of how likely it is to support life like us, at least in our opinion. Other thinking life might have a completely different physical, chemical, and biological derivation, likely impossible in our universe; OTOH, it's almost certain that there's other life in our universe, using other energy gradients than our oxygen-rich atmosphere supports. I won't be surprised to find simple life in Jupiter (and yes, I meant "in," if you know anything about Jupiter you know that's appropriate). I'll frankly be surprised if there's no life there. It's a very rich environment with many potential flows to be tapped. OTOH I won't be surprised if we don't recognize it as "life" at first. Hopefully there's no one smart there to get pissed off and mount an extermination mission against the mites from the awful hellish Third World. Kidding. But only somewhat.

 

The point is, even in our own universe's constants and physical laws, we can see more than one way for "life" to evolve, and even "intelligence." What Linde and Susskind propose is that many universes with all kinds of different physical laws can occur. Why are you, then, surprised that there is this universe that supports thinking beings, whatever that means, here and now, since all kinds of universes occur all the time? I would say if there is Eternal Inflation that every different kind of universe is being explored all the time. In fact, we are not unusual, but inevitable. And we will always occur in a universe like enough to this one. Leave the cream cheese in the fridge long enough and it will eventually demand the vote.

 

Linde has universe fluctuations popping into existence all the time all over the universe. Obviously, thinking beings will only evolve in universes that support them. This is a lemma. Why do you deny it? It's obvious.

Edited February 22, 2014 by Schneibster