Is String Theory the Ultimate Theory of Everything?

[Hossam Halim]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

 

[phinds]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

String theory at this point is not right OR wrong, it is simply a hypothesis that has no experimental evidence but which would explain a lot of stuff very nicely if it DOES turn out to describe reality.

Why would you want to abandon the search for a theory of everything? Do you not care about knowledge?

 

[Hossam Halim]

I meant we should search for the theory of everything with different thinking and to leave string theory as there are 2 experiments falsify it

 

[George Jones]

I meant we should search for the theory of everything with different thinking and to leave string theory as there are 2 experiments falsify it

Which two experiments falsify string theory?

 

[phinds]

I meant we should search for the theory of everything with different thinking and to leave string theory as there are 2 experiments falsify it

As George requested, you MUST back up such a statement with citations otherwise it is just an unsubstantiated personal theory.

 

[Hossam Halim]

Google this : ( string theory fails test )

 

[ZapperZ]

Google this : ( string theory fails test )

Sorry, but this is insufficient.

When you are trying to back up your argument, you must provide proper citation. Asking people to search for the source to support your point should not be done. Google search will turn up both valid and dubious sources. Which one did you use?

Please provide clear, valid references as soon as possible, or this thread will be closed.

Zz.

 

[Hossam Halim]

http://www.simonsfoundation.org/quanta/20121120-as-supersymmetry-fails-tests-physicists-seek-new-ideas/
http://io9.com/5714210/string-theory-fails-first-major-experimental-test
http://www.math.columbia.edu/~woit/wordpress/?p=3338
http://www.rareuniverse.org/scienceblog/No_Supersymmetry20121205.shtml
http://m.slashdot.org/story/145130

 

[PAllen]

All of these are of the following nature:

- Had they been found, they would have added support to (but not confirmed) string theory
- Not finding them does not even remotely disprove string theory

All of the sources you provide are of dubious reliability, or strongly biased.

 

[ZapperZ]

http://www.simonsfoundation.org/quanta/20121120-as-supersymmetry-fails-tests-physicists-seek-new-ideas/
http://io9.com/5714210/string-theory-fails-first-major-experimental-test
http://www.math.columbia.edu/~woit/wordpress/?p=3338
http://www.rareuniverse.org/scienceblog/No_Supersymmetry20121205.shtml
http://m.slashdot.org/story/145130

Please re-read the PF Rules that you had agreed to. Pay attention to the type of sources that we consider as valid.

Not knowing your background, I will assume that you are not familiar with how things are done in science. Valid sources require a DIRECT citation of either well-established standard text/references, or a publication in our accepted peer-reviewed journals. Personal websites and blogs (even by Woit) do not constitute as valid sources. If you used this, then you are using 2nd, 3rd, or even 4th hand news.

This may be an "ordinary" forum, we are try to adhere to the higher standards on the quality of discussion. This means that references and sources must be of the same standard. This hopefully will prevent discussions at the level of tabloid journalism where dubious sources and any and all garbage are in. It also forces YOU to pay attention to where you are getting your information, and hopefully, educate you on how science is practiced.

Zz.

 

[ChrisVer]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

As already pointed out, string or M theory are just theories - they haven't been disproved or confirmed, because they exist far away from our experimental reaches, and their phenomenological results haven't been found yet (however that's a very difficult way to "disprove" the theory, more oftenly, you are just going to disprove one model out of the theory or something like that).

I'd quote Feynman for the "theory of everything" thing, because asking whether we should search or not for a "theory of everything" is more a philosophical question... we are just exploring nature, if there happens to be a "theory of everything" so be it, if there doesn't so be it- we are just seeking for our own answers.

I don't think physicists at the moment do research on string theory (Glashow's viewpoint?). That's something mathematicians or string theorists do. Physicists are trying to find phenomenological results out of it.

 

[micromass]

I'd quote Feynman for the "theory of everything" thing, because asking whether we should search or not for a "theory of everything" is more a philosophical question... we are just exploring nature, if there happens to be a "theory of everything" so be it, if there doesn't so be it- we are just seeking for our own answers.

Here you go:

https://www.youtube.com/watch?v=Eyynpf8x74I

 

[Ilja]

String theory at this point is not right OR wrong, it is simply a hypothesis that has no experimental evidence but which would explain a lot of stuff very nicely if it DOES turn out to describe reality.

Would it really explain at least something?

There is an old joke, that according to string theory our universe is exceptional: It is the only one which string theory is unable to explain.

Why would you want to abandon the search for a theory of everything? Do you not care about knowledge?

The main problem with string theory is that the focus of research capabilities on string theory leaves no place for any other, independent search for a theory of everything.

 

[Bill_K]

There is an old joke, that according to string theory our universe is exceptional: It is the only one which string theory is unable to explain.

I was going to post a joke about String Theory, but there were too many of them.

I meant we should search for the theory of everything with different thinking and to leave string theory as there are 2 experiments falsify it

Judging by your indirect references, the two results you're referring to are:

1) The LHC failed to find evidence for Supersymmetry. This only means that the mass of any supersymmetric partners would be beyond the reach of the LHC, about 1 TeV. There were good reasons for hoping that Supersymmetry would show up at relatively low energies, but even though it did not, it's still a reasonable possibility at higher energy.

2) The LHC failed to find micro black holes. This would have been evidence for large extra dimensions, a somewhat far out idea.

String Theory does not really have anything to say about physics at LHC energies, so these two results neither confirm or invalidate it.

 

[phinds]

The main problem with string theory is that the focus of research capabilities on string theory leaves no place for any other, independent search for a theory of everything.

Now that's just silly. No one area of study precludes any other area of study.

 

[ChrisVer]

Although Supersymmetry is a very nice theory, it's even more elusive than string theory...
Because we always expect to find it at some scales, yet it always avoids our detection hahaha.., At least you know that for strings the energies are unreachable and you only search for evidences of it, however for susy you know very much less (even the mass of Higgs is within the limits of MSSM+radiative corrections (<130GeV).
Nevertheless, don't forget some historical facts. When people first proposed the top quark, they were expecting to find it at ~50-70GeV (sorry I don't remember the exact energy). Of course, it finally appeared at ~170-175 GeV.

Of course there are searches outside string theory... However, during several eras in physics, there are some reasons why people like a theory more than others- because it seems more consistent/predictive. That was one of the reasons QCD dropped away string theory for some decades. But again it's a matter of personal view (some people like string theorists, some others don't consider them to be physicists- as I stated above Glashow belongs to the 2nd group).

Also the person who will come and tell you that he has the theory that describes everything, either his theory is wrong or he won't be a physicist hahahaha (joke)

 

[DrClaude]

Now that's just silly. No one area of study precludes any other area of study.

Now that's just naive.

I said that tongue in cheek, but Lee Smolin has argued (in his book The Trouble with Physics, among other places) that the stronghold of string theory has has stifled research in other theories of quantum gravity, through funding and tenure.

 

[MathematicalPhysicist]

I was going to post a joke about String Theory, but there were too many of them. Judging by your indirect references, the two results you're referring to are:

1) The LHC failed to find evidence for Supersymmetry. This only means that the mass of any supersymmetric partners would be beyond the reach of the LHC, about 1 TeV. There were good reasons for hoping that Supersymmetry would show up at relatively low energies, but even though it did not, it's still a reasonable possibility at higher energy.

2) The LHC failed to find micro black holes. This would have been evidence for large extra dimensions, a somewhat far out idea.

String Theory does not really have anything to say about physics at LHC energies, so these two results neither confirm or invalidate it.

What are the limits on the mass of supersymmetric partners?

I mean, in the future we might have a faster particle accelerator, and they may argue the same argument as you do now, that we need a faster accelrator.

If they don't have some falsifiable limits on the bounds of the masses, then it's not even a theory.
It may even postulate that the energies are infinite, in which case you can never really know if the theory is right or wrong.

 

[PAllen]

What are the limits on the mass of supersymmetric partners?

I mean, in the future we might have a faster particle accelerator, and they may argue the same argument as you do now, that we need a faster accelrator.

If they don't have some falsifiable limits on the bounds of the masses, then it's not even a theory.
It may even postulate that the energies are infinite, in which case you can never really know if the theory is right or wrong.

String theory makes very definite predictions about physics at the Planck energy. That is still like zero compared to infinite energy. However, it might as well be infinite compared to current technology.

 

[MathematicalPhysicist]

String theory makes very definite predictions about physics at the Planck energy. That is still like zero compared to infinite energy. However, it might as well be infinite compared to current technology.

What is the interval of required energies?

I understand that 1 Tev is in the lower end.

 

[craigi]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

Although string theory has taken many twists and turns and many physicists have concerns about the amount of research effort put into it, which could be directed towards other theories of quantum gravity, I think this has been over exaggerated in popular writings, recently.

It's popular to note that string theory has been in development for decades and hasn't yet been confirmed by experiment, but it's also important to note that it hasn't been excluded by experiment either. In fact, to disprove it at low energies, where almost all observational data is gathered, would involve disproving QFT itself, which would be much more problematic.

Amongst other things, string theory has given us the AdS/CFT correspondence, which although it is still conjecture, is widely accepted in theoretical physics and has found uses in our understanding QFT and black holes.

Is string theory a ToE? I'd say probably not because it doesn't tell us how the vacuum of our universe is selected, but it's certainly a useful mathematical description, which could form a subset of, or a limiting case of, a ToE.

 

[ChrisVer]

What are the limits on the mass of supersymmetric partners?

I mean, in the future we might have a faster particle accelerator, and they may argue the same argument as you do now, that we need a faster accelrator.

If they don't have some falsifiable limits on the bounds of the masses, then it's not even a theory.
It may even postulate that the energies are infinite, in which case you can never really know if the theory is right or wrong.

The limits for mass particles don't come from Supersymmetry I guess, they come from the models of Supersymmetry. So models can of course be wrong-
I remembered the value- when the top quark was proposed (right after the discovery of bottom), the models we made proposed that it should have a mass of roughly 17GeV... they didn't find it there, so they said it must be around 30, 40, 50GeV the most... The top quark appeared at 170GeV, and from that we get some lesson. Firstly, the nature will show itself up as it is and not as we want it to be. And secondly, we don't know why the top quark must be so heavy.

 

[ChrisVer]

Is string theory a ToE? I'd say probably not because it doesn't tell us how the vacuum of our universe is selected, but it's certainly a useful mathematical description, which could form a subset of, or a limiting case of, a ToE.

Well, since supergravity is the extension of string theory at lower energies, and since sugra gives us the susy breaking mechanism that allows $E_{vacuum}$ to take zero (or almost zero-as we measure it today-) value, isn't that a possible answer to how it's chosen?

 

[MathematicalPhysicist]

The limits for mass particles don't come from Supersymmetry I guess, they come from the models of Supersymmetry. So models can of course be wrong-
I remembered the value- when the top quark was proposed (right after the discovery of bottom), the models we made proposed that it should have a mass of roughly 17GeV... they didn't find it there, so they said it must be around 30, 40, 50GeV the most... The top quark appeared at 170GeV, and from that we get some lesson. Firstly, the nature will show itself up as it is and not as we want it to be. And secondly, we don't know why the top quark must be so heavy.

Wait a minute, how do they know that it's a top quark before detecting it?

I mean presumably it has some properties that were detected and thus they concluded that it's a top quark. What properties are they looking for in supersymmetry that were'nt detected yet?

I mean this enterprise of research can last for decades (unless people who fund this research will be fed up with no experimental results).

This reminds me of the bet:
http://longbets.org/12/

Just less than 6 more years to go.

 

[ChrisVer]

Wait a minute, how do they know that it's a top quark before detecting it?

I mean presumably it has some properties that were detected and thus they concluded that it's a top quark. What properties are they looking for in supersymmetry that were'nt detected yet?

I mean this enterprise of research can last for decades (unless people who fund this research will be fed up with no experimental results).

This reminds me of the bet:
http://longbets.org/12/

Just less than 6 more years to go.

Some I guess didn't expect such a big divergence to the quarks' masses... And since they found the bottom at ~4GeV, they wouldn't expect the next one to be at 170GeV. And models probably were built to give them this result too.. of course they failed, but also we knew there should be the 6th quark after finding the 5th... That's how it works...
We weren't bored of quarks or leptons,and chose to bring about their superpartners to have more fun... SuSy fixes some problems which are pretty strong, as the gauge hierarchy problem (of course next to SuSy there are more candidates)

At the moment?
They are looking at LHC for enough missing energy (that will be LSP leaving the detectors).
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.112.201802

Or cosmological searches, for WIMPs maybe...

 

[PAllen]

What is the interval of required energies?

I understand that 1 Tev is in the lower end.

The Planck energy is 10,000 trillion Tev.

 

[MathematicalPhysicist]

The Planck energy is 10,000 trillion Tev.

Ok, then why do theorists keep working on it?

I see now why Kaku awaits for a pure mathematical solution for this theory, it's pure mathematics.

 

[PAllen]

Ok, then why do theorists keep working on it?

I see now why Kaku awaits for a pure mathematical solution for this theory, it's pure mathematics.

Theorists work on open problems that interest them. The following are some of the open problems in high energy physics:

- SM does not extend consistently to very high energies
- there are a large number of fundamental constants in SM
- at high enough energies, gravity cannot be ignored in particle interactions

In cosmology, a few are:

- the precise character and scale of deviations from isotropy and homogeneity
- the apparent value of the cosmological constant (or acceleration of expansion).
[I hate the term dark energy]
- dark matter, or the problem dynamics of galaxies and clusters + gravitational lensing
observations

Theorists who work on string theory are following their informed hunch that it provides a framework in which progress on all of these can be made. Theorists who work on other approaches are following different hunches, including the hunch that solutions to some of these problems are independent of each other (or can be treated as such). [The grandiose name TOE has been given to a hypothetical unified theory that solves this particular collection of problems, along with some closely related ones].

Any theorist who thinks string theory remains the most promising approach, should obviously continue to work on it.

 

[ChrisVer]

I think that from PAllen's high energy physics bullets, the last one is the most important for string theory as a mathematical theory (I'm making this distinction because we cannot look at it in a direct experiment...). String theory contains gravity because it contains SUGRA. SuGra is nice because just by dealing with a local supersymmetric theory (on the superspace), you get the gravity because of this relation:
$[ε(x) Q, \bar{Q} \bar{ε}(x)]= 2 i ε(x) \sigma^{\mu} \bar{ε}(x) P_{\mu}$
(maybe I put an extra "i"?)
which tells you that the generators of a local (the ε depends on the spacetime point) supersymmetry transformation create a spacetime translation which depends on the point you've chosen (because the RHS depends on x)- this is the theory of gravity.
So String Theory(theories)>SuGra, can explain gravity without the problems arising from the Standard Model, or without Loop Quantum Gravity approaches which don't care about the perturbative renormalizability (=it's not a fundamental requirement) of the quantum gravity theory. (super)String theory however surpasses this problem (of course it has its own- like the tachyonic modes), and also it contributes to the unification of the forces.

 

[MathematicalPhysicist]

Theorists work on open problems that interest them. The following are some of the open problems in high energy physics:

- SM does not extend consistently to very high energies
- there are a large number of fundamental constants in SM
- at high enough energies, gravity cannot be ignored in particle interactions

In cosmology, a few are:

- the precise character and scale of deviations from isotropy and homogeneity
- the apparent value of the cosmological constant (or acceleration of expansion).
[I hate the term dark energy]
- dark matter, or the problem dynamics of galaxies and clusters + gravitational lensing
observations

Theorists who work on string theory are following their informed hunch that it provides a framework in which progress on all of these can be made. Theorists who work on other approaches are following different hunches, including the hunch that solutions to some of these problems are independent of each other (or can be treated as such). [The grandiose name TOE has been given to a hypothetical unified theory that solves this particular collection of problems, along with some closely related ones].

Any theorist who thinks string theory remains the most promising approach, should obviously continue to work on it.

Well, one question that arises is if there is an upper bound on the energy in the universe?

If there is no upper bound, then theories in physics will never end just like theories in maths.

 

[Haelfix]

There is a vast ocean of physics regimes, theories and possibilities that have very little chance of ever directly being probed that are nevertheless possible, plausible and some are almost certainly true or widely suspected by almost every expert (for instance the rh neutrino species and/or magnetic monopoles)

quantum gravity in general seems to resist being measured despite decades of research. For some reason String theory is often singled out amongst the many candidates even though they all share the same property. Indeed, things are actually better for string theory, bc it does make clear predictions in principle if you had access to such a detector (or a good enough observational window into the early universe)..

As for the question, what about physics at even higher energies than the Planck scale, well it's certainly possible to consider but you get into some subtle issues defining what you mean precisely. What type of experiment do you have in mind and exactly what are you measuring?

 

[ChrisVer]

Above the Planck's mass scale, an object having the characteristic Planck length becomes a singularity/black hole.

 

[maddog]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

I remember reading a SciAm article in May 2014, over concern of end to Supersymmetry due to lack of data from LHC. I was not aware of the claim to the "end to string/M theory". Now I did look up in google where in another post you requested to look up "string theory fails test". I found this on the 4th link:

"did-the-lhc-just-rule-out-string-theory"

This plus the other examples kind of clearly show no such "end". I will grant you there are no currently validatable tests for M theory in any form. Does not in and of itself mean that String or M theory could not be viable.

 

[kneemo]

Hello,
Is string theory or M theory wrong ? Isn't it the theory of everything ? Should we continue our research to reach the true theory of everything ? If so, why physicists still research on string theory ?!

First off, M-theory is not yet complete. It's a work in progress and involves very high level mathematics. You must remember that string theory was not originally used to describe quantum gravity. Gravitons, tachyons and string theory's relation to supergravity were found later, as a few brave souls kept working on the theory.

Think of the situation this way: there is a mysterious theory that people are trying to study in our current, limited mathematical framework. At this time, we need to understand mathematics at a much deeper level, to even make progress with M-theory. So far, a generalization of the Langland's program, along with a better mastery of motives and noncommutative geometry, seems to be very helpful in generalizing D=11 supergravity.

 

[nuclearhead]

The trouble with current string theory is that it is only defined perturbably. (That is in terms of series of string diagrams). That is why M-Theory in 11 dimensions is thought to be needed to unite all string theories in a non-perturbative framework. Some things, like the Higgs framework, only make sense non-perturbably so String theory is not necessarily wrong, but is not considered "complete".

Also string theory is defined on a set background space-time whereas it is thought a complete theory should not have the background space-time as an input but as a consequence.

Lastly it is not yet proven that String Theory is necessary. Since it's low energy limit N=8 Supergravity (coupled to E8xE8 Super-Yang Mills) has not proven yet to diverge.

To me M-Theory or at least matrix theory described in terms of D0 branes connected by strings which quantize supermembranes in certain limits and Loop Quantum Gravity described in terms of spin-networks seem remarkably similar in their basic design. Hence foresee a more complete theory as incorporating aspects from both theories.