Can someone explain to me the 11 dimensions of string theory

[MigL]

No, in my opinion and many others, its a cop-out for a wrong or incomplete theory.

 

And again, if there was a baby universe inflating in your pocket, you would definitely know about it as there would be dire consequences. Not just 'echoes' from before or during the inflationary period of the big ang.

[Schneibster]

That was my point; obviously they're not happening around here any more. Make what you will of it. But don't pretend it disproves Eternal Inflation. It just challenges the most naive version of it.

You just don't want to admit that the exact physics of this particular region of spacetime is a random outcome among an infinity (or anyway a significant fraction of 10³⁰⁰) of potential outcomes.

 

Could you explain why, please?

 

Incidentally note please that a universe developing in your shirt pocket would give you radiation burns and constitute a major hazard to life if it were happening all the time around here.

 

But there are two huge voids on either side of us that hint that they spat out everything that makes us up and it coalesced in between them and then the universe froze, sort of. And now everything is just expanding at the same fairly slow rate, which is slowly increasing in the beginning throes of a new exponential expansion that will culminate in an ever-expanding sterile universe, or, perhaps, a new fertile ground for the occurrence of new vacuum bubbles and new universes.

 

The forecast is for things to remain the same for a trillion years or more. After that the expansion will either render the surrounding expanse of the universe and the multiverse sterile, or something unusual will happen.

Edited February 22, 2014 by Schneibster

[Mike Smith Cosmos]

But there are two huge voids on either side of us that hint that they spat out everything that makes us up and it coalesced in between them and then the universe froze, sort of. And now everything is just expanding at the same fairly slow rate, which is slowly increasing in the beginning throes of a new exponential expansion that will culminate in an ever-expanding sterile universe, or, perhaps, a new fertile ground for the occurrence of new vacuum bubbles and new universes.

.

O.k. So we are sitting here between two great voids "bubbles of nothingness " in the Virgo super cluster.

 

These ""bubbles " ?

 

A normal bubble as a kiddie has , is in equilibrium I suppose because something has managed to capture a bit of atmosphere or air , and that amount is pushing outward , in balance to some form of bubble surface tension pulling bubble texture together in all the surface directions so as to make the bubbly bit of the bubble, push inwards in balance.

 

What quite is going on in the "void type " bubbles , sitting out there in the either side of the Virgo supercluster.?

 

Is it something like a vast "gloop " of dark energy pushing out , against a surface tension type of dark matter in a bubble surface type of bubble. On which is pulled the ordinary matter making up the Virgo

supercluster. Or what ?

 

------------ -----------

 

If that were the case, and I do not know if that is how it is currently perceived?

 

Then Gravity would take care of all the local stuff , like helping dust clouds pull in to shape so that soon new stars can be born. Stars pulled into various shapes to make star systems and stars and planets of various forms!

 

While dark energy and dark matter do all the major constructional work of the large structure of the universe , including all it's bubbles, foam .

 

Is this ,how it is ?

 

Mike

Edited February 23, 2014 by Mike Smith Cosmos

[Schneibster]

Well, there was. Whether it's still there is an open question; they're still expanding, because space is, but I haven't seen any research on whether it's at a different rate than everything else is expanding today.

 

Remember that the far side of the largest one is far beyond the post-Big Bang horizon of the universe. We will never be able to see it. The near side is ten billion light years away, or rather was ten billion years ago; it's quite a bit farther by now and accelerating all the time. Pretty soon we won't be able to see the near side of it either.

There's no more something "pushing them out" then there is in a foam of soap bubbles, after the source stops pumping stuff out.

Edited February 23, 2014 by Schneibster

[Mike Smith Cosmos]

 

Remember that the far side of the largest one is far beyond the post-Big Bang horizon of the universe. We will never be able to see it. The near side is ten billion light years away, or rather was ten billion years ago; it's quite a bit farther by now and accelerating all the time. Pretty soon we won't be able to see the near side of it either.

.

What quite is " the far side The largest one" and " the near side of it " .

 

Are you talking about voids ?

[Schneibster]

Are you talking about voids?

[Mike Smith Cosmos]

Are you talking about voids?

I think I might be getting my voids and general foam structure of the universe muddled up ?

 

You sound a bit more clued up about the big structure than me !

 

Mike

Edited February 23, 2014 by Mike Smith Cosmos

[Schneibster]

It's not just a general foam of equally-sized bubbles, in fact it's got voids (bubbles) of every size from galaxy cluster on up well past the largest matter structures. The distribution appears to be fractal, that is, of similar density at many scales on the largest scales.

 

The assumptions of homogeneity and isotropy have been challenged by COBE, then more strongly by WMAP, and are now being overthrown by Planck. Planck sees a huge "cold spot" in the CMBR. Does that sound like it might be a reverse density fluctuation from the formation of a cosmic void to you?

 

Meanwhile, where did all the matter in the voids go? And the answer is, into the "web" of matter and dark matter and extremely high temperature gas that makes up the galaxy clusters, and out of the voids. And that's why there's voids.

 

Maybe they're where universes with bad cosmological constant values formed. They collapsed back into black holes, or went the other way and blew all their matter out into the surrounding space too fast. Maybe our little matter "salient" between two giant voids is the remains of whatever was in them before they exploded. If they exploded. We're not actually in a universe, we're in the detritus of universes that blew up around us. Just an accident.

 

The Schneibsteress has christened this the "brown universe theory."

Edited February 23, 2014 by Schneibster

[Implicate Order]

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.

 

Hi MigL

 

I sense your frustration as I was facing a similar conundrum until recently. For over 8 years I have been swaying between the Loop Quantum Gravity camp and David Bohms hidden variables theory after being dissatisfied with String Theories multi-verse proposition (String theory's Landscape) and it's associated Anthropic principle, which to me (like you) appeared to be a neat cop-out. I have always sought a theory that at least could fully explain the classicality of this universe before entertaining the prospect of considering other universes. The multi-verse proposition did not offer that solution. As each landscape was causally disconnected, no mathematical findings applicable to other universes would necessarily help in understanding our own classical reality. String theory and it's eleventy billion alternatives appeared to be hopelessly drifting into a sea of mathematical obscurity........until recent events with the Holographic Principle and alternate conclusions drawn from String Theory when you treat this theory as frame-dependent...... and I will get to that.

 

With regards to previously discussing LQG, this is in relation to my comments made in the thread "Quantum Entanglement Solar Flare Detection and Transmission" where I reported on the results of Fotini Markopoulou's work in the field of 'Causal Dynamical Triangulations' in post 81.

 

In regards to background dependent or background independent theories, you are correct and my use was incorrect. My apologies. I frequently get this wrong in my head as unlike a pure GR advocate, due to my interest in QM and in particular the properties of vacuum space, I treat space-time as having physical properties, but this is a QM influence and not a GR one. So let's don't go down the old traditional aether debate as my interpretation is strictly QM. Consequently I see the dynamic nature of space-time (a constraint boundary) as a feature of LQG as the background geometry 'depends' on the contents. In my mind I see the traditional background independence of String Theory as a Newtonian description where the background is static in a framework that describes the contents. Your interpretation is more apt as it more faithfully describes GR in that there is no physical medium (space-time) and it is just about the relationships between things described in a coordinate framework coined space-time.

 

...but here I think lies the problem. I think we need to treat both spacetime and its contents as a physical medium but it is frame dependent. A GR advocate would say that space-time is not a physical manifestation and simply a co-ordinate reference system. I beg to differ. I furthermore think that it is not a correct assumption to extend GR to reflect global geometries as this necessitates that there is an external observer out there outside this universe looking in. There is enough suspicion in recent WMAP results to suggest that extending GR to a global definition may be inappropriate. GR I believe is a correct local tool to use and that is contingent on being applicable within the hubble volume (light cone) of a single observer. The conclusions drawn by an observer internal to the universe necessitates a relational perspective being taken with respect to the observations taken when compared to other frames of references. There is no external viewpoint that can actually see 'everything that is going on'. It is therefore incorrect to conclude a block universe as the 'be all and end all to the theory'. If a common frame of reference can be used for both QM and GR (being the extent of the light cone) then both theories can co-exist together and evolve together yet be indeterminate in nature. The local perspective between reference frames is linked by the information that can be derived from observations taken on those diferent frames by c. Shared observations require that each reference frame is causally connected....but I digress.

 

LQG which has arisen from GR has previously been focussed on the geometrical properties of space time and has had very little to say about the nature of space-times contents which has always been string theorys strength.

 

There is a possible way to reconcile the two approaches provided we avoid the multi-verse proposition. What is required however is to recognise that there is an abstract realm out there referred to as the quantum domain within which is embedded a classical 3D and 1T universe that can faithfully be described by both String Theory AND Loop Quantum Gravity. I personally see this is where it is all heading. Whether or not there is a multi-verse out there is actually not the point. What is the point is whether there is an alternate way to view the multi-verse proposition from a new angle which is fully embedded in a single 3D and 1T universe. This way we can get on the same footing between String Theory and Loop Quantum Gravity.

 

Interestingly the change in tide to a frame of reference approach was promulgated by Hawking and Hertog in their ruthless condemning of cosmological approaches that are bottom-up in approach such as string theory. The problem with a bottom up approach is that you commence with a singularity and are immediately caught with the conundrum of trying to deduce which initial state you should commence from in building a cosmological history. You immediately start with an indeterminate number (infinity) and you can see why string theory is caught in a multi-verse proposition. Hawking and Hertog claim (and this is getting traction) that you should adopt a top-down approach from the frame of reference of an observer to determine a causal history. This top down approach from a single frame of reference avoids a singularity at the end. Furthermore, a correct relativistic approach would actually be to adopt a top down approach to determine the causal histories of all observers (points in space-time). Once this is done then in accordance to Feynmans sum of path histories, you can superimpose the wavefunctions of each causal history to obtain a Gods-eye view of space-time histories that are all causally connected provided each cosmological history shares the same causal patch. What is actually being done here is treating a multi-verse proposition as being equivalent to a many frames proposition in a classical 3D and 1T context.

 

You can see that this approach is adopting an equivalent footing to Fotini Markopoulos LQG approach where she inserts light cones at each point in the lattice of quantum space.

 

GR is not simply about the geometric properties of space time. The Einstein equation demonstrates that geometry (Einstein tensor) represents one-side of the equation and it is equivalent to talk in terms of the mass-energy distribution of space-time (its contents given by the stress-energy tensor). Given that LQG seeks to determine how things can arise from the vacuum due to their relationships with quantised space-time then it is helpful to talk in terms of boundary constraints or the contents contained within those boundaries. Wheeler had an expression that the boundary of a boundary is zero. He showed that he equations of GR follow this principle in that the local curvature of space time cancels out the energy and momentum of the mass thats present there. This only occurs however when the boundary is closed.

 

What this is saying is that everything you need to know about what was going on in the interior of some region of space-time is fully described by the boundary. So black holes and their boundaries may be an ideal candidate to use in searching for clues in how unite both String Theory and Loop Quantum Gravity.

 

..anyway about recent events. Whilst we can generically talk about the string theory camp as advocating the String theory landscape, some in the field disagree with this approach and are seeking a 3D and 1T alternative. It is Raphael Bousso himself, the originator of the string theory landscape idea with Joe Polchinski , who sees deep flaws in the multi-verse proposition and argues vehemently with multi-verse advocates such as Linde. Susskind with his debate with Stephen Hawking that 'won the black hole wars' is turning the tide in he String Theory camp away from irreconcilable multi-verses towards a 'frame-dependent viewpoint in a 3D and 1T context with the complementarity principle.

 

In dealing with black holes and their horizons, the battle lines between Hawking and Susskind were drawn. Either QM needed to give, or GR needed to give. This actually was a battle between String Theory or LQG. The only way to preserve both positions was in how to treat the dilemma faced between two different frames of reference and the results of their conclusions about whether or not information was contained on the event horizon or whether or not information was lost into the black hole.

 

For very large black holes, an inertial observer (riding an in-falling elephant) would simply follow the geodesic in free fall and should not experience anything 'different' when passing through the event horizon. They would not be aware of any horizon at all and according to GR they just will be free-falling (no forces) in vacuum space. Once past this 'hidden boundary' information is lost from the external region.

 

For the accelerated observer outside the black hole that watches the elephant as it makes it's way towards the event horizon, they will observe an event horizon with associated entropy. They will see the elephant get stretched from trunk to tail and slow down as it approaches to be ultimately torched by the entropy of the event horizon. We have a paradox here for both GR and QM. In one interpretation the elephant is dead and smeared over the event horizon and with the other the elephant is alive and well inside the event horizon. In one interpretation information about the state of the elephant is lost to the external system and in the other, information is spread across the event horizon.

 

The only way out of this conundrum to avoid a breakdown of both QM or GR was to adopt the Complementarity Principle. That is to say that either one interpretation OR the other interpretation were correct and that one interpretation AND the other interpretation were NOT correct. This was achieved by ensuring that each interpretation had to be frame dependent and this was the huge break-through that has shaken up the String Theory Camp, put questions on the multi-verse proposition and forced relativism into its picture. Both interpretations are right but in one interpretation we see things emerge from the vacuum such as a boundary with entropy, particles and heat while from the other frame of reference, these features do not emerge. The observer is simply following the geodesic in empty space.

 

What this has done is bring the holographic principle into fully fledged form in the string theory camp and provided it is frame dependent, you do not need a multi-verse description. Leonard Susskind despite being an advicate of the multi-verse is now questioning this notion and recognising the importance of frame-dependence.

 

A De-Sitter universe can be explained in terms of either the boundary of the universe or its contents dependent on the frame of reference of the observer. With space-time accelerating expansion, unlike black holes, it is the inertial observer who sees the boundary and it is the accelerating observer who does not.

 

 

I hope MigL that this explains why I see that both camps are actually significantly contributing to unification as opposed to travelling their separate paths. You can see recent discussions on this bt the proponents themselves on Edge.org. To nail the point home we have had an approach called String Theory starting with defining things from bottom-up and ending up with boundary descriptions, while we have had LQG starting from top down commencing with boundary constraints and ending up with things described with light cones embedded in the lattice of quantum space. We have then made String theory frame dependent with the Complementarity Principle and furthermore flipped the theory to be a top down approach like LQG. We still have the 10D and 1T dimensioins of string theory to deal with but we could possible extract the 7 microscopic dimensions and shuffle them off to Hilbert space and then we will appear to be now on the same footing where both approaches are different interpretations of the same universe but both aproaches are embedded in a higher abstract mathematical geometry.

PS. Once again thanks to Amanda Gefter for helping me see the light as this interpretation is not my own but an interpretation arising from discussions held between Amanda Geftner, her father and the swathe of physicists from both camps that she has interviewed. I urge anyone that is interested to look at her book "Trespassing on Einstein's Lawn".

Edited February 23, 2014 by Implicate Order

[MigL]

Thanks I.O.

I wasn't aware of any of these ongoing developments.

You've provided a lot to look into, and think about.