What are strings made of?

[Herringbone]

At one time, I read where strings were vibrating bits of space-time. In "The Elegant Universe" TV program, they were described as vibrating bits of energy. In "The Elegant Universe" book they are described as consisting of fundemental "string stuff" and that questioning their composition really has no meaning.

OK... so now I'm (even more) confused.

[Ambitwistor]

The book description is the closest to the truth. They are certainly not vibrating "bits of spacetime"; I don't even know what that would mean. They aren't "bits of energy", either; they have energy.

Strings aren't made up of anything more fundamental; they are the fundamental building blocks --- everything is made up of them. Strings have a size and shape and a tension, and that's about it for classical physical properties (neglecting technicalities like conformal fields, Chan-Paton factors, etc.).

[Herringbone]

Yeah, "vibrating bits of spacetime or energy" never made sense to me either.

The string's (incredibly huge) tension is an interesting property however. Tension in a classical string is created by the electromagnetic force. What is the force creating tension in a superstring?

Is there another fundamental force? It seems that the vibration of a superstring would involve either the oscillation of this force or the oscillation of the Calabi-Yau space dimensions.

[Ambitwistor]

Tension in a classical string is created by the electromagnetic force. What is the force creating tension in a superstring?

There isn't any; tension is fundamental.

Is there another fundamental force? It seems that the vibration of a superstring would involve either the oscillation of this force or the oscillation of the Calabi-Yau space dimensions.

The vibration of a string is pretty much just like the vibration of a classical string, postulating the "tension" as an elementary property of the string. String vibrations aren't due to any oscillation of space; they occur even in flat background spacetimes.

[Loren Booda]

Strings could consist of probability space, rather than spacetime.

[Mike2]

Originally posted by Herringbone

The string's (incredibly huge) tension is an interesting property however. Tension in a classical string is created by the electromagnetic force. What is the force creating tension in a superstring?

Is there another fundamental force? It seems that the vibration of a superstring would involve either the oscillation of this force or the oscillation of the Calabi-Yau space dimensions.

Tension is a force. Force is the gradient of a scalar potential field. Perhaps this is where the "background" potential comes in. Now, they suppose that the tension is constant along the string. But that seem more of a stipulation than a derivation.

See comments in the thread:

diff EQ on strings, check out the math

[madcat11]

Doesn't your definition of tension (with regard to strings) necessarily have to rely on the way in which the term is used?
For example, tension can be looked at as coming from without or from within the thing... it can be a force applied or a force inherent, the act of movement or the condition of the already moved or moving...

Or - and I think this is probably the closest to the norm where strings are concerned - it can be a measure of that which something already contains, i.e., condition of stretch, tautness, elongation, position, measure of vibration or even balance.

And sometimes, it's only sematics... we all know what we're talking about; it's just getting that concept across to someone else, right?

[Herringbone]

Doesn't your definition of tension (with regard to strings) necessarily have to rely on the way in which the term is used?

The classical definition of tension that I'm thinking of is the internal force within something that act against a set of external forces working to pull the thing apart. For example it's the EM force providing tension in my guitar string that prevents it's breaking from the pulling force the guitar and I exert on it.

Which raises the question: can superstrings break under their tension and what happens if they do? The sound my guitar makes when I break a string isn't very musical.

There isn't any; tension is fundamental.


This seems to be the key point. The string tension force would appear to be the fundamental force since it is from the actions of this force that gives rise to all the other forces.

[Ambitwistor]

Which raises the question: can superstrings break under their tension and what happens if they do?

Strings have have a uniform tension (perturbatively), but they can break.


This seems to be the key point. The string tension force would appear to be the fundamental force since it is from the actions of this force that gives rise to all the other forces.

There isn't a "string tension force" in the sense that there is, say, an electromagnetic force: there is no force field permeating space. Tension is just one physical property of a string, like its length.

[quartodeciman]

"String stuff"?? Shades of Sagan! Remember "star stuff" from Cosmos? "We are made of star stuff." So, I guess star stuff is made of string stuff.

------

Ed Witten at Santa Barbara in 1996 answered the question as follows:


(an approximation)
---
In our theory, all matter is explained in terms of strings. Without a better theory, it makes no sense to ask then what a string is. It will probably take another half century to understand the present theory in a sensible way.
---

Here, you can listen to his whole talk and look at his overheads.

UCSB KITP public lecture "Duality, Spacetime and Quantum Mechanics" --->
http://online.itp.ucsb.edu/online/plecture/witten/

[lethe]

Originally posted by Ambitwistor
The book description is the closest to the truth. They are certainly not vibrating "bits of spacetime"; I don't even know what that would mean.

i m not quite sure how to interpret that statement either, but i sometimes say it too.

the reason is that i consider the geometry of spacetime to be a coherent state of gravitons. gravitons are stringy excitations, therefore spacetime is somehow a coherent state of string.

in this sense, i can think of a string as a bit of spacetime, no? i, like you, am not quite sure what to make of the statement. so this mean that spacetime is no longer a manifold? that certainly doesn t appear from the math.

what do you think?

[madcat11]

Re: tension

Since you can't experimentally 'pluck' strings, like you can a guitar string, you have to look at them indirectly.

Swartz and Scherk used the postulated properties of a graviton and its messenger particle to calculate that the particle's transmitted force is inversely proportional to its string tension. So you have the direct relationship of 1/(2pa') where a' is alpha prime and is equal to the square of the string length scale.

And since the graviton is so weak, the tension is enormous (actually the Planck tension or around 1039 tons...) And this huge tension means the string contracts to the Planck length (very very tiny...)

Also, high tension means high energy string. So a string's energy is determined by two things: its vibration and its tension.

So, if you have tension directly related to both length and vibration of a string, it becomes an inate part of the string's nature and not some outside 'input.' So maybe the analogy of a guitar string is inaccurate, since you have to pluck a guitar string to make it vibrate, as well as having to first string it up to give it the proper tension...

[Herringbone]

There isn't a "string tension force" in the sense that there is, say, an electromagnetic force: there is no force field permeating space.

The string tension “force” sort of reminds me of a pre-Einstein description of a force, which got me thinking.

My guitar string is essentially held together by the exchanges of photons between the atoms of the metal. If I were to cut one end of the string while it were under tension, the other end wouldn’t “know” it until a later time determined by the speed of light.

Since the tension in a superstring is fundamental and is not transmitted by a boson limited to the speed of light, when a string breaks is there a limitation as to how fast that information is transmitted across the entire string?

[pelastration]

I see a rubber band (elastic) on my table. I am amazed about i's level of activity. Maybe it's due to the air pressure in Europe but it doesn't move or osccilates at all. The rubber band lays still. Like in a relaxed state.
Now on the most basic Witten level this must be different? Amazing! It's almost like magic.
Is it also different in the States?

[Ambitwistor]

If you postulate a relativistic string, which is what is done in string theory, then influences cannot propagate faster than c.

In fact, effects on a string propagate at a speed


v = \sqrt{\frac{\tau}{\mu}}


where τ is the tension and μ=m/L is the mass per unit length. But in string theory, the tension is equal to the energy per unit length, so

\tau = E/L = mc^2/L = \mu c^2

and thus

v = \sqrt{\frac{\mu c^2}{\mu}} = \sqrt{c^2} = c

[pelastration]

Originally posted by Ambitwistor
The book description is the closest to the truth. They are certainly not vibrating "bits of spacetime"; I don't even know what that would mean. They aren't "bits of energy", either; they have energy.
And how do they get energy? For a mobile phone?[!:)]

Originally posted by Ambitwistor
Strings aren't made up of anything more fundamental; they are the fundamental building blocks --- everything is made up of them.
So they ARE?
That's it? [6)]

[lethe]

Originally posted by Herringbone
The string's (incredibly huge) tension is an interesting property however. Tension in a classical string is created by the electromagnetic force. What is the force creating tension in a superstring?


the whole thing becomes a lot less mystifying if instead of calling it "tension", you call it mass per unit length.

a particle has mass (which labels its irrep of the Poincaré group), so the string (which is going to replace the particle) should have a mass too, and a mass per unit length.

[pelastration]

Originally posted by lethe
the whole thing becomes a lot less mystifying if instead of calling it "tension", you call it mass per unit length.

a particle has mass (which labels its irrep of the Poincaré group), so the string should have a mass too, per unit length.
So - as Ambitwistor said - "strings aren't made up of anything more fundamental" there was mass from the beginning. Nice[6)]

[pelastration]

Originally posted by Herringbone
At one time, I read where strings were vibrating bits of space-time. In "The Elegant Universe" TV program, they were described as vibrating bits of energy. In "The Elegant Universe" book they are described as consisting of fundemental "string stuff" and that questioning their composition really has no meaning.

OK... so now I'm (even more) confused.
Now Herringbone I think this is one of the best - fundamental questions - on this forum about string.
I could ask also 'How strings are created?', but that's even more fundamental magic. [6)]
After 35 years ST the experts don't know. They even say that's a question for half of the 21 Century. See any logic? [*(]

[Herringbone]

So, if you have tension directly related to both length and vibration of a string, it becomes an inate part of the string's nature and not some outside 'input.' So maybe the analogy of a guitar string is inaccurate, since you have to pluck a guitar string to make it vibrate, as well as having to first string it up to give it the proper tension...

Well, I agree that the guitar might not be the best analogy but after all the pop representations of string theory its kind of hard not to go there.

And aside from the obvious difference of open vs closed loops and fundamental string stuff, I can see some analogies, albeit extremely superficial. Now of course we're talking about one of those perfect guitars you find in physics books where there are no frictional losses, etc...

You don't actually have to pluck a guitar string to make it vibrate. Just increasing the tension quickly will start it vibrating as the string length decreases. This could be considered analogous to the energy of the Big Bang (?) causing strings under their enormous tension to shrink down to be contained by the curled dimensions which could have given them their initial "input".

The analogy is that as I add energy into my guitar string by turning the tuning peg, I'm causing the string to "shrink" down to be constrained by the space defined by the guitar's body which also causes the string to vibrate.

With no losses the guitar string would indefinitely continue to produce a spectrum of vibrations determined by the shape of it's guitar "space" as well as the length and tension of it's strings just as a superstring produces a spectrum of vibrations determined by the string's length and tension as well as the shape of the tiny Calabi-Yau space that constrains it.

[pelastration]

Originally posted by Herringbone
The analogy is that as I add energy into my guitar string by turning the tuning peg, I'm causing the string to "shrink" down to be constrained by the space defined by the guitar's body which also causes the string to vibrate.
What 'force' turns the peg and where is it fixed to make 'turning' possible?

[pelastration]

Herringbone,

I will explain more: Have you ever put in a bath (filled with water of course) a piece of wood with a screw inside and tried to screw that screw deeper inside the wood? [g)] It will keep you busy for about 10 years till the water left. You can start this experiment today [t)].

[Herringbone]

What 'force' turns the peg and where is it fixed to make 'turning' possible?

Like I said, not the best analogy but I see it like this:

The source of energy that turns the peg is me. I create the "lil' Bang" for my guitar string. The tuning peg is fixed to the "space" of my guitar string's 'universe' (the guitar) which serves to constrain the final size of the string.

When I turn the peg a certain direction, I'm changing the guitar string's universe in such a way that the string's tension increases, its size decreases and it begins to vibrate.

But all this analogy stuff is probably getting off topic so...

[Herringbone]

I will explain more: Have you ever put in a bath (filled with water of course) a piece of wood with a screw inside and tried to screw that screw deeper inside the wood? It will keep you busy for about 10 years till the water left.

Hi pelastration,

Not sure I get your analogy but no problem with the experiment.

I'll just turn up the air conditioner until the water freezes and boom, the screw is screwed.

Or (providing the conditions didn't prohibit it) I'll just use an electric screwdriver that provides enough speed and torque to make to water seem like it was frozen (due to friction and inertia).

[:)]

[pelastration]

Originally posted by Herringbone
Hi pelastration,

Not sure I get your analogy but no problem with the experiment.

I'll just turn up the air conditioner until the water freezes and boom, the screw is screwed.

Or (providing the conditions didn't prohibit it) I'll just use an electric screwdriver that provides enough speed and torque to make to water seem like it was frozen (due to friction and inertia).

[:)]
[:D] but in fact [s(] ? Is that a Black & Decker your using? Those Baltimore guys come always with something dangerous! Electric tolls in water!
But of course the strings will also be limited in oscillations. What do they do at Kelvin zero?
On your second point: I am rather sceptic. Maybe you should make from this 'gedanken' experiment a real bathroom experiment [t)]. To have more fun, you can add some extra soap to find some spacefoam bubble facts! Success. Keep us informed.

[diverz]

"Strings" are just manifestations of energy. Vibration is a form of energy in itself because energy by itself is formless and without mass.

All in all, everything in the universe is made up of energy. "Vibrations" and combinations of "Vibrations" make up the assortment of particles we see.

Thats my opinion.

What is mass? Mass feels solid isn't it? Why does it feel solid? Does solid itself have any meaning or is it just a word to describe the sensation we human beings feel when we touch something solid?

[Ambitwistor]

Originally posted by diverz
"Strings" are just manifestations of energy. Vibration is a form of energy in itself because energy by itself is formless and without mass.

All in all, everything in the universe is made up of energy. "Vibrations" and combinations of "Vibrations" make up the assortment of particles we see.


I really don't like it when people treat energy (or mass) as some kind of substance that things are made out of. Energy and mass are just some physical properties that objects can have, among many others (charge, momentum, angular momentum, etc.)

Thats my opinion.


Mass feels solid isn't it? Why does it feel solid?

Matter in solid form feels solid. That's because the matter in your hand doesn't interpenetrate the matter in an object. And that's because the matter in your hand repels the matter in an object (due to fermionic and electrostatic repulsion).

[diverz]

Originally posted by Ambitwistor
I really don't like it when people treat energy (or mass) as some kind of substance that things are made out of. Energy and mass are just some physical properties that objects can have, among many others (charge, momentum, angular momentum, etc.)

Thats my opinion.

You don't like it just because you feel that energy and mass are just some physical properties? Then what do you feel that strings are made of?

[Ambitwistor]

Originally posted by diverz
You don't like it just because you feel that energy and mass are just some physical properties?

I don't "feel" that energy and mass are physical properties. Energy and mass are physical properties. Particles and strings have energy, but it's not correct to say that they "are" energy or are "made up of" energy; energy is just one of many physical properties that a particle or string may have.

Then what do you feel that strings are made of?

String's aren't made out of anything more fundamental, because they are fundamental. This is just like how quarks and leptons in the Standard Model aren't made out of anything more fundamental, because they are fundamental.

[diverz]

How sure are you that strings are fundamental? I mean people used to think that atoms are fundamental but discovered there's something more to that.

[Ambitwistor]

Originally posted by diverz
How sure are you that strings are fundamental? I mean people used to think that atoms are fundamental but discovered there's something more to that.

There isn't any experimental evidence that strings even exist, let alone are fundamental. But in string theory, strings are fundamental. (If you try to break a string to see what it's made of, you just get two strings.)

[quartodeciman]

One has to start somewhere with something. Anything capable of generating all phenomena at higher levels must have an intricate set of attributes built into it, a spectrum of potentialities. Someone else can demand furthur explanation of the basis for all these attributes. But it isn't likely anyone can provide a significant theory that offers explanation all the way down.

------
"The world is held up by the trunks of three giant elephants."
"What holds up the elephants?"
"The elephants are standing on the shell of an even larger tortoise."
"What does the tortoise stand on?"
"It stands on the shell of yet an even larger tortoise."
"What does..."
"Sorry, it's tortoises from here on."

[diverz]

Originally posted by Ambitwistor
There isn't any experimental evidence that strings even exist, let alone are fundamental. But in string theory, strings are fundamental. (If you try to break a string to see what it's made of, you just get two strings.)

Ok I agree with you that strings are fundamental in string theory. The point I'm trying to make is if strings can be broken down further, its not fundamental anymore. However, we can stop this discussion at this point because there's no experimental evidence.

Now I have another question. Do you think energy can be broken down into smaller parts?

[Ambitwistor]

Do you think energy can be broken down into smaller parts?

Energy isn't an object that can be broken into parts; your question makes no more sense than asking whether, say, momentum can be "broken into parts".

[diverz]

What is defined as being fundamental? If I'm not mistaken, it means something that cannot be broken down further? Correct me if I'm wrong.

[Ambitwistor]

What is defined as being fundamental? If I'm not mistaken, it means something that cannot be broken down further?

It doesn't really have a rigorous definition in physics. But your description is roughly correct, depending on what you mean by "broken down".

[diverz]

That means energy is fundamental according to the fact that it can't be broken down into simpler forms and particles aren't fundamental because they can be broken down further.

In string theory, it is established that strings are fundamental.

Hmm..... Interesting.

Can 2 different things exhibit identical properties? Or maybe I should phrase it this way -----> Is it possible for strings and energy to be fundamental building blocks and yet be different at the same time since your view is that energy is a property of strings?

[Ambitwistor]

That means energy is fundamental according to the fact that it can't be broken down into simpler forms

Like I said, it doesn't make sense to speak of energy as "fundamental" in this sense. Energy is not an object, so it doesn't even make sense to talk about whether it can be "broken down" into parts or not.


Is it possible for strings and energy to be fundamental building blocks and yet be different at the same time since your view is that energy is a property of strings?

You don't take "pieces of energy" and stick them together to make things. Energy is not a "building block", fundamental or otherwise. Energy simply is not a physical object or substance, it's a property (among many) that a physical object can have.

[diverz]

Ok then in the words of your argument, can you tell me what really is physical/object?

[FilipKunc]

i'm not a physicist, but i don't think that this question can be answered before we understand the whole string theory... in fact we might never answer this question, just like we can't explain "where did the uniwerse come from?"- we can only tell how it began, but not why it began, or where it came from...
i have a question: do you think that it's possible to unify space and matter (just like einstein unified space and time)...? we can't call something "the theory of everything" if it leaves space, in which everything takes place, and matter, that fills the space as two separate things. that's just my opinion.

[diverz]

Well I was just gonna mention space.

What do you guys think of space? Standard human understanding/definition of space is that it is emptiness. Nothing. Absolutely empty.

Now my question to you is ----> How can something exist and yet is empty (no mass no substance no nothing.... ie. a vacuum)?

This is getting interesting [:)]

I wanna see what you guys think.

[diverz]

Perhaps I should phrase it this way ----> What makes space? Space just can't exist for the sake of existence isn't it? I know you guys are all rational beings who are into science. You don't just accept "its simply there" as an answer. Now try to answer my question and I'll see if I agree with your point of view.

[diverz]

Bump for Ambitwistor's point of view/comments [:)]

[pelastration]

Originally posted by diverz
Now my question to you is ----> How can something exist and yet is empty (no mass no substance no nothing.... ie. a vacuum)?

1. See spacetime as unbreakable and elastic.
2. Let it penetrates itself.
3. A new quantum package (QP)is created with two separate but joined layers.
So it's still empty but the spacetime layers will oscillate locally in a different way.
4. Such QP's can interact and build up other QP's. They all are still empty.
5. A human is thus a house build by empty packages.
6. The human observer can see only other QP's that are resonant to his observing QP's system.

[hypnagogue]

Originally posted by Ambitwistor
There isn't any experimental evidence that strings even exist, let alone are fundamental. But in string theory, strings are fundamental. (If you try to break a string to see what it's made of, you just get two strings.)

Is there any theoretical limit to how small a string you can create by breaking a larger string? Or can the process theoretically proceed ad infinitum?

[hypnagogue]

Originally posted by Ambitwistor
I really don't like it when people treat energy (or mass) as some kind of substance that things are made out of. Energy and mass are just some physical properties that objects can have, among many others (charge, momentum, angular momentum, etc.)

This is an interesting take. However, it seems as if this position leaves us with a conglomeration of physical properties without a central object to "have" them in the first place. If there is no such thing as "substance," then what is the object that has physical properties, and by what mechanisms does it 'enforce' its ownership of these physical properties? (Sorry if that's a little metaphorical, but I can't think of a better way to phrase it for now.)

[Mike2]

Originally posted by diverz
Perhaps I should phrase it this way ----> What makes space? Space just can't exist for the sake of existence isn't it? I know you guys are all rational beings who are into science. You don't just accept "its simply there" as an answer. Now try to answer my question and I'll see if I agree with your point of view.


Of course reality must be reducible to logic itself. Physics must be derivable from the principles of reason alone. For otherwise, you are right, it only begs the question as to how the fundamentals came to be. A theory based on the existence of just some particle or field that is not itself justified only give us better engineering, but it is certainly not psychologically satisfying because it leaves questions unanswered. We will not stop until we can say that physics is the result of some description of logic. That is my effort here.

On my Website (http://www.sirus.com/users/mjake/StringTh.html#consider) I show how the principles of logic and probabilities can be described graphically is some sort of "sample space". Then I show that we can impose a coordinate system on it. And then we can describe a type of string theory as being the propogation of some open "event" in sample space.

But this in itself does not answer your question, where did it all come from. The question reduces to how the manifold of space-time came into existence in the first place. I've read that no dimensionality can exist at a mathematical critical point where all partial derivatives are zero. But such a point is also unstable, any movement whatsoever will only accelerate in that direction. So it seems that the universe started from such a critical point. And the manifold of reality has been growing ever since. It's curious that general relativity predicts an expanding manifold of space-time.

[Jeebus]

I know its a bot of a "grey" answer but strings are not a predetermined definate in size so we should theorize that a string is in fact made up of smaller strings, and those strings are made up of even smaller strings and so forth. It just keeps going to an inherent fuzziness of open strings that automatically incorporate one of the key ingredients in string theory.

All of physical reality is made out of different states of the superstring. Roughly speaking, each vibrational mode of the string can be thought of as a point particle. Hence, one superstring gives rise to infinitely many local fermion and boson fields. All of the observed bosons and fermions can be cosidered as a vibrational mode of the fundamental superstring. It must be noted that the string is both constituent and interaction. Superstrings can be either open or closed.

I also think that strings could be made or from the inflation of the universe or Gravity differentiates and even symmetries -- but I use this term loosely because there is no given via axioms in theories.

[Mike2]

Originally posted by Jeebus
I know its a bot of a "grey" answer but strings are not a predetermined definate in size so we should theorize that a string is in fact made up of smaller strings, and those strings are made up of even smaller strings and so forth. It just keeps going to an inherent fuzziness of open strings that automatically incorporate one of the key ingredients in string theory.

It might be that closed strings can be made up of smaller closed string on some sort of membrane. If the smaller inside strings cancel at their boarders, then the result is the one larger string on the outside edge.

Maybe that's how strings interact, when one meet another they share a common boarder that cancels to leave only one larger string?

[S = k log w]

How can a string be elemental if it can be cut in to smaller strings,
or for that matter if it can be cut? Wouldn't an absolute findamental be indivisable? If a string needed time or space in which to exist, then how can bit be fundamental? To say that it exists but is fundamental is rather like saying matter exists in the ether

[quartodeciman]

Strings would be fundamental if no matter what you did to them the only possible result were strings. Atoms were once considered the same way. It wasn't so much that atoms were pointlike in size. They simply were thought to be indivisible. As soon as it was realized that smaller bodies that were not atoms (electrons) could be removed from atoms, then atoms weren't fundamental any more.

[selfAdjoint]

But it is true that strings remain strings no matter what you do to them. If you cut them apart you have two strings. If you join two together you have one string. Twisting them, knotting them doesn't change their stringyness, and the whole of string theory accepts the unsplittible stringiness of strings. The theory may be wrong about that, but so far there has appeared no reason to think so.

[Mentat]

Hold on, I thought M-Theory postulated a minimum size (the Planck's size) for all physical entities...wouldn't this mean that you can't "cut" a string any smaller than it already is?

[quartodeciman]

According to Pat Schwartz:

""
The string tension in string theory is denoted by the quantity 1/(2 π a'), where a' is pronounced "alpha prime"and is equal to the square of the string length scale.
""
.
link -->
http://superstringtheory.com/basics/basic3a.html

Tstring = 1/2πα' (string tension from length scale)

Lmin ~ 2√α' (minimum length from length scale)

Then Lmin ~ √(2/π)(1/√Tstring)
.

So, is the minimum length bounded below or is the string tension bounded above?

------

bonus: lecture slides on branes.
The Physics of Branes by Sunil Mukhi -->
http://www.ias.ac.in/meetings/annmeet/68am_talks/smukhi/index.html

Branes are more fundamental than strings?

[Loren Booda]

String tension is to mechanical tension as Planck's constant is to angular momentum.

[FilipKunc]

isn't there something called "string coupling constant" which defines (correct me if i'm wrong) how easy it is for a string to divide itself into smaller strings??? if strings have a tension, then it is possible to tear them apart, if one pulls hard enough ;).

[quartodeciman]

Also, open strings can wrap around compact dimensions, even multiple times. So I guess string length is variable.

The wrap count serves as a quantum number?

[lethe]

Originally posted by quartodeciman

The wrap count serves as a quantum number?

yup

[S = k log w]

It has been historically true that one theory of what is the most fundamental conceptual unit of existence had later been challanged by another theory of something even smaller, (and/or larger). I would like to know an elequent 'theory of everything'. Is it possible that there is no fundamental elements/strings/whatever, nor 'theory of everything'? String theory poses one problem for me; when asked, why do strings 'exist'?, the answer, (please correct me if I am wrong), is that strings 'exist' because strings 'exist'. Before (I believe it was Einstein) all 'things' 'existed' in something called the ether (sp?). Einstein had asked, what is ether made from? Isn't saying that strings 'exist' because strings 'exist' like saying strings 'exist' in an 'ether'? That strings 'exist' because strings 'exist' is taking it on faith that strings 'exist' because strings 'exist'. For what reason does this not lead to existentalist angst?

Is there a mathematical proof that there is such a thing as a fundamental?

[Mike2]

Originally posted by S = k log w
It has been historically true that one theory of what is the most fundamental conceptual unit of existence had later been challanged by another theory of something even smaller, (and/or larger). I would like to know an elequent 'theory of everything'. Is it possible that there is no fundamental elements/strings/whatever, nor 'theory of everything'? String theory poses one problem for me; when asked, why do strings 'exist'?, the answer, (please correct me if I am wrong), is that strings 'exist' because strings 'exist'. Before (I believe it was Einstein) all 'things' 'existed' in something called the ether (sp?). Einstein had asked, what is ether made from? Isn't saying that strings 'exist' because strings 'exist' like saying strings 'exist' in an 'ether'? That strings 'exist' because strings 'exist' is taking it on faith that strings 'exist' because strings 'exist'. For what reason does this not lead to existentalist angst?

Is there a mathematical proof that there is such a thing as a fundamental?

We are looking for physical laws that are logical in every way, and which can be described by mathematics. You've seen Venn diagrams used to show how to construct AND's and OR's of logic. And these AND's and OR's can just as easily be describe in a sample space. These spaces can be parameterized with coordinates. And they look very much like the manifolds talked about in physics. AND's and OR's are included in both.

If we ever expect to find mathematical laws of physics that are logical in every way, then we should realize that they will be a description of how events grow in sample space.

We seem tantilizingly close to justifying the geometry of physics. The Action integral is proportional to the surface area of the world sheet. The Lagrangian is the generalized gradient and is equal to zero so that it describes a geodesic, etc. But they have no reason for this geometry other than to say it works. It might be possible to recognize these world-sheets as growing events in sample space, and the geodesics as the most probable direction of its growth. But this would take a leap of faith on their part to believe that there is a logical explanation for everything even if we don't know it yet. How can we escape the conclusion that physic is a mathematical description of logic when we impose the requirement of logic and mathematics on our physics to begin with?

[S = k log w]

Originally posted by Mike2
We are looking for physical laws that are logical in every way, and which can be described by mathematics. You've seen Venn diagrams used to show how to construct AND's and OR's of logic. And these AND's and OR's can just as easily be describe in a sample space. These spaces can be parameterized with coordinates. And they look very much like the manifolds talked about in physics. AND's and OR's are included in both.

If we ever expect to find mathematical laws of physics that are logical in every way, then we should realize that they will be a description of how events grow in sample space.

We seem tantilizingly close to justifying the geometry of physics. The Action integral is proportional to the surface area of the world sheet. The Lagrangian is the generalized gradient and is equal to zero so that it describes a geodesic, etc. But they have no reason for this geometry other than to say it works. It might be possible to recognize these world-sheets as growing events in sample space, and the geodesics as the most probable direction of its growth. But this would take a leap of faith on their part to believe that there is a logical explanation for everything even if we don't know it yet. How can we escape the conclusion that physic is a mathematical description of logic when we impose the requirement of logic and mathematics on our physics to begin with?

We can't "escape the conclusion that physic is a mathematical description of logic when we impose the requirement of logic and mathematics on our physics to begin with". This is my point. How can we avoid agnst? Do all theories lead to questions? It is certainly fun to persue this, but is it possible to find a 'theory of everything'?

[Mike2]

Originally posted by S = k log w
We can't "escape the conclusion that physic is a mathematical description of logic when we impose the requirement of logic and mathematics on our physics to begin with". This is my point. How can we avoid agnst? Do all theories lead to questions? It is certainly fun to persue this, but is it possible to find a 'theory of everything'?

Please see my Website at:

http://www.sirus.com/users/mjake/StringTh.html

where I show how it might be possible to derive physics from logic. If we impose a coordinate system on Venn diagrams and assume a function that tells us whether samples exist or not within a region, then we have the mathematics to describe logic. Then since physical situations are the propositions of logic, and we have a mathematical description of propositions, therefore, we have a mathematical description of physics.

Following the geometry invovled with this scenario, I've come up with something that is beginning to look a lot like string thoery.

[Mike2]

Originally posted by Mike2
If we impose a coordinate system on Venn diagrams and assume a function that tells us whether samples exist or not within a region, then we have the mathematics to describe logic. Then since physical situations are the propositions of logic, and we have a mathematical description of propositions, therefore, we have a mathematical description of physics.

The question comes up as to what physical thing are we sampling with time. What is this density function, where did the boundaries of these events come from, etc?

The answer is that it doesn't matter. Whatever it is, the mathematics will be the same.

[Loren Booda]

For more on LQG, see next month's Scientific American article by Lee Smolin.

[Seafang]

If Strings are THE fundamental building blocks of everything, and they have a 'tension', then does that mean that they are deformable, and how can anything that is NOT built of other smaller things be deformable ?

It would be nice to have a definitive answer on this preferrably from someone who thought these things up in the first place.

And if they aren't deformable, then how does the 'tension' manifest itself; is it just a 'virtual tension' ?

[Mike2]

Originally posted by Seafang
If Strings are THE fundamental building blocks of everything, ...
If any kind of integration is done along the length of the string, then they are adding up infinitesimal portions of something that is physical. This also implies a continuous variable that has physical meaning.

[Seafang]

I found that discussion to be interesting, particularly the question 'is it possible to have a 'theory of everything' ?

To me the mathematics is all pure fiction; we made it up in our heads, and nothing that we discuss in mathematics exists in nature.

Some won't believe that but it is true. there are no points or lines or circles or any of those things in the universe. But there are approximations to them in our models of the universe. The equation for a sphere does not explain the existence of 8000 meter mountains on the surface.

So it may be possible to create a theory (mathematics) of a 'model of everything'. But I doubt that we can ever construct a model that behaves like the real universe.

[Mike2]

Originally posted by Seafang
So it may be possible to create a theory (mathematics) of a 'model of everything'. But I doubt that we can ever construct a model that behaves like the real universe.

right. The mathematics comes from imposing an arbitrary coordinate system over the location of the physical objects which are being considered. The set of objects exists independently of the coordinates we impose. And the math we use is an attempt to describe the relationships we see between these objects.

Since the coordinates are arbitrary, we expect the underlying objects to be described by functions that do not change with whatever coordinate system is imposed. These intrinsic characteristics are "invariant" with coordinate transformations. They are "symmetric" with respect to coordinate changes.

It turns out that this requirement of symmetry or invariance is the only thing we need to discern characteristic values that are conserved and do not change with time or position. And because of that we can know when interactions have taken place and what they produced. For we measure these characteristics to have increased or decreased due to interactions with others. We can know that particular events must have taken place because we can see how things have changed.

[Andthensome]

I think strings are made out of either taffy or mozerella cheese. [o)]

mmmmmm, cheeese. [6)]

[meteor]

I have the book "Three roads to quantum gravity", and it says that strings are composed of little pieces called string bits. I'm not sure if these pieces are fundamental though

[paultrr]

Bits and fragments of space-time, as Smolin tends to term them. Together they form space-time.

[pelastration]

Originally posted by paultrr
Bits and fragments of space-time, as Smolin tends to term them. Together they form space-time.
Hi Paul,

As you remember from superstringtheory.com such concept of Smolin fits into my approach because then the bits (and fragments) are just oscillating spacetime membrane. What appears to us as closed (and open-end) strings may be a mathematical cut of vibrating spacetime peaks (like a circle represents a tube in 2D). You can see what I mean on http://www.mu6.com/stringtheory_peaks.html .

Remember our discussion how only one giant closed string would be identical as a giant spherical membrane? We only needed ONE string to explain all. In the mean time my website developed in graphic presentations such as an image where I point out the similarity of Alan Guth's pocket universes with my holon creation. http://www.mu6.com/spacetime2.html . Guth's false vacuum is then the (non-structural) Prior-Geometry and pocket universes contain then the (structured) duality of holons (Quantum packages/Baskets).

BTW nice seeing your back here ;-)

Dirk

[paultrr]

No, problem. Been mostly buzy on the outside lately and with the holiday and all.

[Mike2]

Originally posted by pelastration
Hi Paul,

As you remember from superstringtheory.com such concept of Smolin fits into my approach because then the bits (and fragments) are just oscillating spacetime membrane. What appears to us as closed (and open-end) strings may be a mathematical cut of vibrating spacetime peaks (like a circle represents a tube in 2D). You can see what I mean on http://www.mu6.com/stringtheory_peaks.html .

You show a portion of a membrane extruding outwards and strings as a slice of this protrusion. My question is what is this plane that is cutting these protruding portions of the membrane?

[pelastration]

Originally posted by Mike2
You show a portion of a membrane extruding outwards and strings as a slice of this protrusion. My question is what is this plane that is cutting these protruding portions of the membrane? Mike2,
I just try to represent 'a string' as a 2D projection of an oscillating 3D membrane peak. A closed string could then represent the avarage vibration of such 'peak'. This a personal vision (different from official ideas). I just try to find out if the actual (official) concept of strings fits with the idea that strings are just part of the brane and - in second stage - can couple to become QM-baskets (second picture). The spacetime is IMO non-breakable and can not be teared or cut. So the 'cutting' is just a graphical 'slide' and 'top-view' projection. Sorry for the confusion.

[paultrr]

Now you've hit the real crux of the ultimate question being asked by Science, "Where did it all come from?". Most of us suspect Nature is its own origin of itself. Now, that could imply that some form of space-time, or at least its primary building blocks have always been around(ala Hawking's Instanton of time), or that while the first is true a loop in time(ala Gott)brought about our present space-time structure,or that multiple vacuum states collided(ala coliding branes, etc), or you can resort to philosophy and religion and invoke the "God" equation. At the present time we've simply not got enough of a grasp on what is the proper road to a quantum gravity to actually determine exactly the right path. But the right question does start exactly at what you've just asked.

[Mike2]

Originally posted by pelastration
Mike2,
I just try to represent 'a string' as a 2D projection of an oscillating 3D membrane peak.

This seems to imply that there is no instantaneous string state; there is only the world sheet as a whole, which completely closes at the tip of the peeks. Otherwise, there would be an instantaneous string state at present time. Then the question arises as to what plain is slicing the protrusions to produce the string at the present time.


A closed string could then represent the avarage vibration of such 'peak'. This a personal vision (different from official ideas). I just try to find out if the actual (official) concept of strings fits with the idea that strings are just part of the brane and - in second stage - can couple to become QM-baskets (second picture).


Have you been able to produce a mathematical description of all this, yet?

[paultrr]

One aspect of what strings are made of goes back to Feynman diagrams.
Feynman diagrams are graphs that describe processes where particles interact, like this:

\ / Two particles come in,
\ /
----- they exchange a virtual particle,
/ \
/ \ and two particles go out.

The number we compute from a Feynman diagram gives the amplitude
for the process to occur. Now this all relates to Loop Quantum Gravity, which, it is assumed for the sake of argument at present, relates to String Theory as far as the building blocks go.

In the quantum field theory called "phi^3 theory", the
diagrams are trivalent graphs with three edges meeting at
each vertex, like the one above. The basic building blocks are the
edge:


---------


and the vertex:

\ /
\ /
\ /
|
|
|

We can draw these in any rotated fashion. The parameter
corresponding to the edge is called the "mass" of the particle in
this theory, because in quantum theory, a particle's mass affects
what it does when it's just zipping along. The parameter corresponding to the vertex is called the "coupling
constant", because it affects how likely two particles are to couple
and give birth to a third. So the focus here, and this is where the bits and shards of space-time come from is that each of these loops formed by edges and vertexes is a fragment of a bigger composite we call space-time.

Its rather like a jigsaw puzzle. You do not have a complete picture till you put all the peices together. Those like Smolin say this type of modeling is devoid of a background. But personally one could argue that bits and peices of a background still imply a background. Smolin's main point was that the larger fabric we call space-time is absent from this type of picture or model.

One can actual see rather simply how one could build up a string from a bunch of stringy fragments. Regular everyday string is formed by combining many smaller bits of fabric. However, it is correct that even this model does not fully answer where did these fragments come from. Perhaps a prior mixing or ripping apart of a prior space-time? Actually, the list goes on when it comes to ideas.

[paultrr]

Parden the diagrams. They did not translate right to here. But Feynman diagrams abound for you to get the idea from.

[paultrr]

The most shocking outgrowth of the physics of branes has been the Maldacena conjecture. This conjecture states that M-theory subject to particular boundary conditions is in fact equivalent to some supersymmetric Yang-Mills theory on a manifold of smaller dimension. One example is the so-called AdS/CFT correspondence, in which string theory with boundary conditions matching the ten-dimensional manifold given by the product of 4+1 Anti-DeSitter space and a five-sphere (AdSsub5 x S^5) is conjectured to be equivalent to 3+1-dimensional super Yang-Mills theory.

The concepts involved in LQFT simply discribe what makes up these small structures themselves and in essence discribe how the String, that is the particle as an extended object, is formed.

Part of the question being asked is what is the most fundamental part of nature? Is it the String, the Branes, or the Loops?

In addition to strings, M-theory contains a zoo of higher dimensional objects; e.g. 2-dimensional membranes (aka 2-branes), 3-dimensional `3-branes', etc. An object with p spatial dimensions is known as a p-brane. These branes are now thought to be as fundamental as the string itself. The various branes are related to fundamental strings by powerful symmetries known as dualities.

The branes can form up into Strings and Strings can also form up into branes, but both objects are composed of something more primary themselves. Take String and one can weave a fabric which well term a brane or sheet. Yet, that same sheet can be decomposed into its basic string which in turn can be decomposed into its basic fabric parts itself.

If the quantum loops are actually the basic fabric then they could be seen as the most basic parts to be found in nature. However, at the present this has yet to be fully worked out or proven. Also any solid quantum theory will have to also account for where these basic bits of fabric actually came from. So a deeper fundamental question one can start with is Loops of what?

A starting point might be concentrating on the coupling constant issues. For example, the beta function has been calculated to four loops, in QED and in general matter flavor QCD/SQCD or SU(N_c). But even in QED, where Abelian Ward identities cancel divergences of wave function and vertex leaving only vacuum polarization logs, that doesn't tell you what "the running coupling" does at high orders. But the fact that this coupling exists can cause us to ask the question of coupling of what or to what?

We need to decide whether we're talking about a physical coupling, related to an amplitude, with the entire loop correction amplitudes resummed gauge invariantly; or an unphysical parameter in perturbative expansion in some particular renormalization scheme, perhaps in an asymptotic approximation that keeps only leading logs at high momentum. Also, we can have spacelike or timelike momentum transfer, depending on the physical process, and the subleading momentum terms depend on that.
But one could start this process of questioning by focusing on spacelike and timelike momentum transfer. In general with momentum we have energy coupling from one point to another. Coupling tends to imply direction to this energy flow which in turn implies a tensor field at play. But we can also have a simulation of a tensor field’s end product of direction via differences in a scalar field like the measurement of temperature. Under entropy we have flow of energy from a high temperature region into a lower temperature region. The result is a net coupling of energy from one region to another defined by tensor and scalar fields interacting.

This then sort of implies a picture where the basic building blocks of the cosmos are bits of energy. But then we have to further define exactly what energy is.

We measure energy via time, movement, etc in units expressing work. But then using time we are somewhat rather forced right back to a system with one of the original parts of the background invoked again when the whole idea was to get away from the background and form a background independent model.

Might seem a long way to bring up a point and indeed it is a long fashion to do so. But what is being shown here is that its hard to answer a question about the origin of something who’s very nature depends upon the background of time and space itself and who’s origin point would seem to be beyond some predetermined T=0 point.

[pelastration]

Originally posted by paultrr
.... This then sort of implies a picture where the basic building blocks of the cosmos are bits of energy. But then we have to further define exactly what energy is.

We measure energy via time, movement, etc in units expressing work. But then using time we are somewhat rather forced right back to a system with one of the original parts of the background invoked again when the whole idea was to get away from the background and form a background independent model.

Might seem a long way to bring up a point and indeed it is a long fashion to do so. But what is being shown here is that its hard to answer a question about the origin of something who’s very nature depends upon the background of time and space itself and who’s origin point would seem to be beyond some predetermined T=0 point.

Thanks Paul for this very interesting analysis and overview of the various parameters involved with the fundamental question about the creation of all. String, brane , loops, coupling, .... energy, .... lots of interaction, and we have to make conceptual choices all the time such as the question: physical/unphysical.

But indeed that energy brings us back to the background.
To solve that ... don't we have to start with a unified starting concept: the background itself?

I believe the quest must start at the top. And then that background must be processed into the complexity that we see today around us, in you and everyone.
The background (das 'Feld') should include the gravity effect: stress and tension of the background. We may not throw away the gravity effect during our journey, since that is the only force that is "ALL the time" present. Where other forces change faces and values ... that inter-connective gravitational effect works all the time.

[paultrr]

I think in general you do, though we might argue where exactly to start there. Here is the real crux of the problem somewhat reflective of Kant's own views also:

We have synthetic a priori knowledge of the spatial and temporal forms of outer and inner experience, grounded in our own pure intuitions of space and time; and to argue that transcendental idealism, the theory that spatiality and temporality are only forms in which objects appear to us and not properties of objects as they are in themselves, is the necessary condition for this a priori knowledge of space and time. Basically, these forms, weither they be string, loops, or branes are not in themselves an actual substance of reality. They are more our constructs by which our minds can get a handle on the sub-atomic world and come to understand how this world works.

Our conceptions of space and time cannot be divorced from experience of objects, because any such experience presupposes the individuation of objects in space and/or time, and that although we can represent space or time as devoid of objects, we cannot represent any objects without representing space and/or time. No matter how small one chooses to go as far as our breaking down these constructs one always returns in one fashion or another to the aspect of time and space. What we can hope to create is a fundamental theory or construct that is not dependent upon space and time.

In general, through the theory of general relativity we have a working model of just such a construct where the interplay of geometry has allowed us to begin to fathom what was once thought of as an action at a distance effect into an on stage performance of the interplay of different fields coming together to form the background we call space-time. The center stage actor in all this is energy expressed as matter telling space-time how to bend and warp and that warpage in turn telling energy how to move. So the primary question to start with is why is there energy in the first place?

[alexsok]

On a related note, does anyone think Penrose's original idea still holds a firm basis these days?

His original suggestion was that quantum state reduction occurs at the Planck scale, where spin-networks encode proto-consciousness... so it's a quantum mechanical process and when the wavefunction collapses, we "experience"...

[paultrr]

Jack Sarfatti, even though he follows Bohm's pilot wave model, tends to at least by implcation support such. Personally, while I believe quantum effects do have implications for the subject of consciousness I tend to rather like avoiding them in general discussions of physics. However, Penrose was a man well ahead of his time in many ways so I would not fully discount his ideas out either.

[pelastration]

Originally posted by Mike2
.... there is only the world sheet as a whole, which completely closes at the tip of the peeks. Then the question arises as to what plain is slicing the protrusions to produce the string at the present time.
...
Have you been able to produce a mathematical description of all this, yet?
Thanks Mike2,
indeed that's a possible entry. Since the specialists found a number of mathematical significant formulaes ... but have no concept behind ... we can use our own creativity.
No, I have not explored math's behind ... and that's not my job. I am just a conceptor, an inventor interested in real things. With such membrane material I could build the world and life and consciousness we see today.

[Bera1989]

The idea that strings are made of energy does not satisfy me. To me, it makes more sense that strings are made of space which move through time and other dimensions. Strings are all conected and influencing each other. Knots of "waves interacting with each other" make up subparticles. Therefore at this level we can be considered as an interactivity among multiple dimensions; what makes existence or matter looks like a living(strings are in constant motion) bunch nothing.

[Dmitry67]

On a related note, does anyone think Penrose's original idea still holds a firm basis these days?

His original suggestion was that quantum state reduction occurs at the Planck scale, where spin-networks encode proto-consciousness... so it's a quantum mechanical process and when the wavefunction collapses, we "experience"...

No, wavefunction never collapses.