Is String Theory A Waste Of Time?

[Juan R.]

I only bought one string theory textbook. Different chapters in the book purport to prove why N dimensions are necessary for a consistent theory. The only problem is that N is not a constant but changes from chapter to chapter.

Carl

Very good point!

In fact the history of dimensions is

4D, 5D, 26D, 10D, 11D, ...

According to B. Greene some string theorists are now working in the posibility of more than one time dimension whereas others claim that the fail of compactification may indicate that there are still unknown 4D-versions of "string" theory.

Also the size of strings changes from "chapter to chapter" from "infinitely" small (Planck) to mm range to again "infinitely" small to infinitely large. There is a version that says that compactified dimension are the usual 4D ones, etc.

The rest of "theory" is also chapter-dependant and even book-dependant or author-dependant!

 

[Juan R.]

Now I’m no String or M theory expert, in fact I don’t see how they could be correct. But based the quality of the people and the work they have done, I trust and I believe the ideas were rigorously formed. And for me the idea of 10 or 11 dimensions was reasonable reached in this case. So for me I feel they have met the standard. Even though I do not believe in extra dimensions myself I feel it’s only responsible to accept the higher standard. Therefore if I want to show strings to be wrong, and there is something better, I must understand how they made the mistake of assuming the extra dimensions. If I can’t take the responsibility to do that, then why should anyone take a new idea seriously?

I just find this a more reasoned and logic approach to the issue rather than just cobbling a bunch of ideas together with no proofs, and no explanations of how the others made the wrong conclusions.

Is that easy to do – of course not it's harder, nobody promised easy.

RB

This sounds like the main argument for studying string theory that some string theorists use: "Because Witten believes on it".

That is not a scientific argument.

The "quality" of people is a subjective concept and, moreover, is not guarantee of a good work. Look for example the history of QFT, almost all great guys Schrödinger, Dirac, etc. did the wrong work and a new generation of young people did QFT. In fact, this argument against string theory has been recently used by Dyson.

Regarding the "quality" of the work they have done, i could say that the quality is very low, with lot of wrong details that are corrected after of decades. Material known in other fields is introduced decades after in string theory. In concrete points, I can assure that the quality of Seiberg's work on NC geomstry is low, the quality of Schwartz's work on unitarity is low, the quality of Witten's work on QM foundations is low, the quality of Nanopoulos' work on the arrow of time problem is low, etc.

So for me I feel they have met the standard.

Curiosly the standard in quantum gravity research is not that.

Therefore if I want to show strings to be wrong, and there is something better, I must understand how they made the mistake of assuming the extra dimensions.

Curiously science does not work on that way. Are string theorists who may show that universe is 11D! Curiously string theorists have shown nothing and none of their initial promises has been done after of more than 30 years!

It is time for exploring other alternatives.

 

[RandallB]

It is time for exploring other alternatives.

Well at least that's one point we completely agree on.
I just hope and even expect that a good alternative will prove strings wrong by show how/why it appeared to them there should be multi D's. I'd even expect proving so can be helpful.
RB

 

[RandallB]

"Euclidean" in this context refers to any geometry where the line element $$ds^2 = g_{ab}dx^adx^b$$ is positive definite. So you can have Riemannian geometry that is Euclidean. The line element of GR is not positive definite, because the "time" term is a different sign from the "space" terms.

And "background independent" is a property of the physics together with the geometry, not the kind of geometry alone. If the physics acts on the geometry, and the geometry determines the physics, so there is self-interaction, then you have background indpendence.

So is GR consided background indpendent ??
Does "The line element of GR is not positive definite" address this issue?

The Lee Smolin link (Thanks for finding Marcus)
http://arxiv.org/abs/hep-th/0507235
Provides a firm argument the GR is “relational” or background independent.
At least where “warping” is concerned.
Is this generally accepted as the case or is this a “debated point” ?

 

[CarlB]

In fact the history of dimensions is
4D, 5D, 26D, 10D, 11D,

If you attribute the hidden dimensions in string theory to internal degrees of freedom between constituents of the supposedly fundamental particles, then the varying number of hidden dimensions is an obvious indication that the number of constituents varies between the particles.

If spin-1 bosons have more internal constituents than spin-1/2 fermions, (as one might expect if all these particles were condensed from fermionic subparticles) it is quite natural that in string theory, the fundamental bosons would have a larger number of hidden dimensions than the fundamental fermions.

The quarks and leptons seem to require 10 or 11 dimensions in total, while the various gauge bosons require 26. (I'm reading Polchinski.) These numbers are about right for the spin-1/2 fermions to be composed of three fundamental subparticles, while the spin-1 bosons are composed of six. That is, three subparticle fermions would have a total of something around 12 degrees of freedom, while six subparticles would have about 24.

Various authors have proposed that the quarks and leptons are condensed states and the number of subparticles is frequently given as three. My own proposal is along this line, but is somewhat radical:
http://brannenworks.com/PHENO2005.pdf

Carl

 

[Juan R.]

If you attribute the hidden dimensions in string theory to internal degrees of freedom between constituents of the supposedly fundamental particles, then the varying number of hidden dimensions is an obvious indication that the number of constituents varies between the particles.

If spin-1 bosons have more internal constituents than spin-1/2 fermions, (as one might expect if all these particles were condensed from fermionic subparticles) it is quite natural that in string theory, the fundamental bosons would have a larger number of hidden dimensions than the fundamental fermions.

The quarks and leptons seem to require 10 or 11 dimensions in total, while the various gauge bosons require 26. (I'm reading Polchinski.) These numbers are about right for the spin-1/2 fermions to be composed of three fundamental subparticles, while the spin-1 bosons are composed of six. That is, three subparticle fermions would have a total of something around 12 degrees of freedom, while six subparticles would have about 24.

Various authors have proposed that the quarks and leptons are condensed states and the number of subparticles is frequently given as three. My own proposal is along this line, but is somewhat radical:
http://brannenworks.com/PHENO2005.pdf

Carl

However, in string theory, the hidden dimensions are not related to internal degrees of freedom on a 4D universe.

"then the varying number of hidden dimensions is an obvious indication that the number of constituents varies between the particles."

I do not understand to you here. The varying number of hidden dimensions is just historical one. In superstring theory, the number of dimensions is 10 and 11 in the new M theory, but is not 10D for some particles and 26D for others. Superstring theory is a priori valid for both bosons and fermions. Only the old bosonic string theory is for 26D.

I do not know if fermions are elementary or composed objects. Nobody know that, still let me highlight that in superstring, brane and M theory fermions are elementary objects, of course are vibrational states of the p-brane but are not composed of collection of branes. They are the brane itself.

 

[CarlB]

However, in string theory, the hidden dimensions are not related to internal degrees of freedom on a 4D universe. ... I do not understand you here. The varying number of hidden dimensions is just historical one. In superstring theory, the number of dimensions is 10 and 11 in the new M theory, but is not 10D for some particles and 26D for others. Superstring theory is a priori valid for both bosons and fermions. Only the old bosonic string theory is for 26D.

I don't mean to argue that string theory is correct, but instead to point out that the dimensional regularization that leads to various assumptions of dimensions in string theory is an argument that can also be applied to the hidden dimensions arising from multi particle bound states.

Since string theory, like Kaluza-Klein, only deals with the lowest modes, there will inevitably be many different physical arrangements that will give those same modes. In other words, by ignoring all but the lowest energy modes, the mathematics problem of defining the physical situation from the spectrum is severely under constrained. What I'm suggesting is that the modes that correspond to the standard model can be written as the lowest modes resulting from composite particles. I think that this can be done in a manner compelling in its simplicity. But when you're done with this, there may be a way to solve the string theory vacua problem, at least on a particle type by particle type basis.

Carl

 

[Juan R.]

I don't mean to argue that string theory is correct, but instead to point out that the dimensional regularization that leads to various assumptions of dimensions in string theory is an argument that can also be applied to the hidden dimensions arising from multi particle bound states.

Since string theory, like Kaluza-Klein, only deals with the lowest modes, there will inevitably be many different physical arrangements that will give those same modes. In other words, by ignoring all but the lowest energy modes, the mathematics problem of defining the physical situation from the spectrum is severely under constrained. What I'm suggesting is that the modes that correspond to the standard model can be written as the lowest modes resulting from composite particles. I think that this can be done in a manner compelling in its simplicity. But when you're done with this, there may be a way to solve the string theory vacua problem, at least on a particle type by particle type basis.

Carl

Aha!

Well, unfortunately i cannot help to you here. I am a bit confused on the question of unification and i do not know which could be the best (promising!) way.

- Perhaps composite particles.
- Perhaps pure geometric arguments on 4D on style of Connes program.
- Etc.

Unfortunately, i cannot valuate your proposal now. I am just focusing in quantization of pure gravity and spacetime.

 

[sssddd]

i would really like to know the background of the guy who says string theory is a waste of time.

 

[RandallB]

i would really like to know the background of the guy who says string theory is a waste of time.

He has promoted links to canonical science in earlier posts here that might help. I could never make heads or tails of it though. Maybe you’ll have more luck.