String theory is what?

[hackenslash]

Although you could really call it a speculative model, containing a whole heap of hypotheses and an intricate web of mathematical reasoning that few can grasp in its entirety...

No argument here.

I'm not really against it, just waiting for it to generate experimentally testable predictions, whether via cosmological data, or high energy particle physics.

It has made testable predictions. I often come across people not making the connection between Turok and Steinhardt's 'brane-worlds' model (not suggesting that this is the case here), but that model is rooted in M-Theory, and it has made testable predictions, which I will come to.

Not at all since the people working there don't think LHC could turn up evidence that would distinguish string theory. So no perhaps in the long distant future but the energy scales that would distinguish string theory are simply enormous and unobtainable. String Theorists disagree but then they would.

There's a documentary where the physicists are asked to give a practical evaluation of the likelihood of CERN confirming strings, I'll try and find it if anyone is interested. It was a Horizon I think with that guy who appears to be on our TVs everywhere with anything to do with physics or astronomy atm, although I forget his name OTTOMH.

That would be 'Do You Know What Time It Is?'. with Brian Cox.

As for the LHC providing evidence for M-Theory, the model proposed by Turok and Steinhardt has made predictions that, in principle, can be tested at the LHC, in the form of gravitational waves. Now, it isn't the only model that predicts gravitational waves, but in this model they are significantly blue-shifted. It may be that the LHC doesn't give us the requisite energies, of course, because if these strings are anywhere near the Planck scale, it would require a particle accelerator about the size of the solar system to probe, but they are still, again in principle, testable and falsifiable. Of course, the LHC can't provide complete falsification because of the scale limitations, but it could provide confirmation of those predictions if the LHC's GWDs show these waves.

As for what the people at CERN think about the probability of turning up this evidence, that's a bit of a moot point, since we all know that there are many, many detarctors of M-Theory in the scientific community. This boils down to an issue of belief, which doesn't really enter into the equation. I say the same to them that I say to any of the howling (and I do mean howling) detractors. Let's wait and see what the experimental data turn up, shall we?

[Coito ergo sum]

A theory, no I don't think so, show me how I am wrong.

I like this thread topic as the adherents are like fanatics and the counterargument is fundamentally logically untouchable. So what makes science and the scientific method? Maths or evidence and maths?

Yes, string theories are theories. In general, string theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings. These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin. The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.

By way of example, early string theory called the "dual resonance model" was based upon the observation that the amplitudes for the s-channel scatterings matched exactly with the amplitudes for the t-channel scatterings among mesons and also the Regge trajectory. Dual resonance model string theory later took a back seat to quantum chromodynamics which is a theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons making up hadrons (such as the proton, neutron or pion). It is the study of the SU Yang–Mills theory of color-charged fermions (the quarks). Quantum chromodynamics is a quantum field theory of a special kind called a non-abelian gauge theory. It is an important part of the Standard Model of particle physics. A huge body of experimental evidence for quantum chromodynamics has been gathered over the years. Here is a description of experimental tests for quantum chromodynamics: http://en.wikipedia.org/wiki/Quantum_ch ... ntal_tests

Granted, the jury is still out and there are many different "string theories" and some have more evidence than others, and some are basically pure mathematics. But, they are theories.

[The Dagda]

A theory, no I don't think so, show me how I am wrong.

I like this thread topic as the adherents are like fanatics and the counterargument is fundamentally logically untouchable. So what makes science and the scientific method? Maths or evidence and maths?

Yes, string theories are theories. In general, string theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings. These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin. The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.

By way of example, early string theory called the "dual resonance model" was based upon the observation that the amplitudes for the s-channel scatterings matched exactly with the amplitudes for the t-channel scatterings among mesons and also the Regge trajectory. Dual resonance model string theory later took a back seat to quantum chromodynamics which is a theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons making up hadrons (such as the proton, neutron or pion). It is the study of the SU Yang–Mills theory of color-charged fermions (the quarks). Quantum chromodynamics is a quantum field theory of a special kind called a non-abelian gauge theory. It is an important part of the Standard Model of particle physics. A huge body of experimental evidence for quantum chromodynamics has been gathered over the years. Here is a description of experimental tests for quantum chromodynamics: http://en.wikipedia.org/wiki/Quantum_ch ... ntal_tests

Granted, the jury is still out and there are many different "string theories" and some have more evidence than others, and some are basically pure mathematics. But, they are theories.

No they are not. EOS.

A theory requires a body of empirical evidence, it is currently barely a hypothesis.

[Coito ergo sum]

A theory, no I don't think so, show me how I am wrong.

I like this thread topic as the adherents are like fanatics and the counterargument is fundamentally logically untouchable. So what makes science and the scientific method? Maths or evidence and maths?

Yes, string theories are theories. In general, string theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings. These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin. The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.

By way of example, early string theory called the "dual resonance model" was based upon the observation that the amplitudes for the s-channel scatterings matched exactly with the amplitudes for the t-channel scatterings among mesons and also the Regge trajectory. Dual resonance model string theory later took a back seat to quantum chromodynamics which is a theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons making up hadrons (such as the proton, neutron or pion). It is the study of the SU Yang–Mills theory of color-charged fermions (the quarks). Quantum chromodynamics is a quantum field theory of a special kind called a non-abelian gauge theory. It is an important part of the Standard Model of particle physics. A huge body of experimental evidence for quantum chromodynamics has been gathered over the years. Here is a description of experimental tests for quantum chromodynamics: http://en.wikipedia.org/wiki/Quantum_ch ... ntal_tests

Granted, the jury is still out and there are many different "string theories" and some have more evidence than others, and some are basically pure mathematics. But, they are theories.

No they are not. EOS.

A theory requires a body of empirical evidence, it is currently barely a hypothesis.

There are string theories that do have empirical evidence, as I noted. The "observations" and the "experimental tests" for dual resonance model and quantum chromodynamics is empirical evidence.

[The Dagda]

A theory, no I don't think so, show me how I am wrong.

I like this thread topic as the adherents are like fanatics and the counterargument is fundamentally logically untouchable. So what makes science and the scientific method? Maths or evidence and maths?

Yes, string theories are theories. In general, string theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings. These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin. The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.

By way of example, early string theory called the "dual resonance model" was based upon the observation that the amplitudes for the s-channel scatterings matched exactly with the amplitudes for the t-channel scatterings among mesons and also the Regge trajectory. Dual resonance model string theory later took a back seat to quantum chromodynamics which is a theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons making up hadrons (such as the proton, neutron or pion). It is the study of the SU Yang–Mills theory of color-charged fermions (the quarks). Quantum chromodynamics is a quantum field theory of a special kind called a non-abelian gauge theory. It is an important part of the Standard Model of particle physics. A huge body of experimental evidence for quantum chromodynamics has been gathered over the years. Here is a description of experimental tests for quantum chromodynamics: http://en.wikipedia.org/wiki/Quantum_ch ... ntal_tests

Granted, the jury is still out and there are many different "string theories" and some have more evidence than others, and some are basically pure mathematics. But, they are theories.

No they are not. EOS.

A theory requires a body of empirical evidence, it is currently barely a hypothesis.

There are string theories that do have empirical evidence, as I noted. The "observations" and the "experimental tests" for dual resonance model and quantum chromodynamics is empirical evidence.

They do not distinguish it from other models, I'm sorry but if the Higgs boson is a hypothetical particle and strings are a theoretical particle wherein lies the difference. It's as simple as that until we see a physically discreet manifestation of strings that can be explained by no other theory in experiment, string theory is barely even a hypothesis. The only people who think it is are String Theorists and those who are caught up in the cult status of what is currently a proto science. It's time they put up or shut up with an experiment that puts strings on the map before they claim it is a theory they need to have repeatable peer reviewed experimental manifestations that could not be explained by the standard model or LQG or x.

[Coito ergo sum]

A theory, no I don't think so, show me how I am wrong.

I like this thread topic as the adherents are like fanatics and the counterargument is fundamentally logically untouchable. So what makes science and the scientific method? Maths or evidence and maths?

Yes, string theories are theories. In general, string theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings. These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin. The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.

By way of example, early string theory called the "dual resonance model" was based upon the observation that the amplitudes for the s-channel scatterings matched exactly with the amplitudes for the t-channel scatterings among mesons and also the Regge trajectory. Dual resonance model string theory later took a back seat to quantum chromodynamics which is a theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons making up hadrons (such as the proton, neutron or pion). It is the study of the SU Yang–Mills theory of color-charged fermions (the quarks). Quantum chromodynamics is a quantum field theory of a special kind called a non-abelian gauge theory. It is an important part of the Standard Model of particle physics. A huge body of experimental evidence for quantum chromodynamics has been gathered over the years. Here is a description of experimental tests for quantum chromodynamics: http://en.wikipedia.org/wiki/Quantum_ch ... ntal_tests

Granted, the jury is still out and there are many different "string theories" and some have more evidence than others, and some are basically pure mathematics. But, they are theories.

No they are not. EOS.

A theory requires a body of empirical evidence, it is currently barely a hypothesis.

There are string theories that do have empirical evidence, as I noted. The "observations" and the "experimental tests" for dual resonance model and quantum chromodynamics is empirical evidence.

They do not distinguish it from other models, I'm sorry but if the Higgs boson is a hypothetical particle and strings are a theoretical particle wherein lies the difference. It's as simple as that until we see a physically discreet manifestation of strings that can be explained by no other theory in experiment, string theory is barely even a hypothesis. The only people who think it is are String Theorists and those who are caught up in the cult status of what is currently a proto science. It's time they put up or shut up with an experiment that puts strings on the map before they claim it is a theory they need to have repeatable peer reviewed experimental manifestations that could not be explained by the standard model or LQG or x.

You said there was "no" empirical evidence. There is empirical evidence.

There is no single theory that is really strong enough to have become generally accepted, and all the theories we have are almost certainly wrong to some extent. However, that doesn't make them "not theories." That makes them weak theories. They are not hypothesis, because there have been observations and tests, as I noted above.

[The Dagda]

They do not distinguish it from other models, I'm sorry but if the Higgs boson is a hypothetical particle and strings are a theoretical particle wherein lies the difference. It's as simple as that until we see a physically discreet manifestation of strings that can be explained by no other theory in experiment, string theory is barely even a hypothesis. The only people who think it is are String Theorists and those who are caught up in the cult status of what is currently a proto science. It's time they put up or shut up with an experiment that puts strings on the map before they claim it is a theory they need to have repeatable peer reviewed experimental manifestations that could not be explained by the standard model or LQG or x.

You said there was "no" empirical evidence. There is empirical evidence.

There is no single theory that is really strong enough to have become generally accepted, and all the theories we have are almost certainly wrong to some extent. However, that doesn't make them "not theories." That makes them weak theories. They are not hypothesis, because there have been observations and tests, as I noted above.

Like what? You keep saying there is evidence of this but show me an experiment?

The String Theorists are pretty much going to be on the back foot until they put up something that says this is not just the standard model or x model this is discrete because x doesn't have this or this.

There is a theory that has become strong enough its called the standard model which predicts the missing Higgs. It is the mainstream. Your proto theory is still at the planning stage now you have to test it.

[lpetrich]

1. Supersymmetry

How would you test for this in what experiment have you shown this?

Still not yet, though the LHC may change that situation.

Supersymmetry is theoretically attractive for several reasons:

It handles spin-0 particles well. They don't get a mass proportional to the momentum cutoff of the calculation of 1-loop and higher-loop interactions.

It relates particles with different spins, meaning that it can help explain why there are particles with several different spins in our Universe.

The Minimal Supersymmetric Standard Model does the best gauge unification at GUT energies, better than the plain Standard Model or most proposed extensions of it.

The MSSM has a particle that's a potential dark-matter particle.

2. Extra dimensions

How do you test for dimensions we can't see nor probably never will? It disappears into x is not a proof.

The same as what one would do for anything that is not directly apparent. To try to find testable predictions, and see how they compare with observation and experiments.

I remember an old joke to the effect that the theorists' job is to piss off the experimenters with wild theories in order to provoke them into making experimental tests.

[Nautilidae]

Like what? You keep saying there is evidence of this but show me an experiment?

We have given several examples of testable predictions made by string theory. However, you do nothing but ignore our points.

1. Supersymmetry

If we smash particles together and find SUSY particles, supersymmetry has been tested. It's as simple as that.

2. Extra dimensions

This can be tested in a number of ways. One method would involve discovering micro black holes in the LHC.

3. Holographic principle.

This can be tested by observing a phenomenon called "holographic noise". If the holographic principle is correct, quantum fluctuations may create background noise. This can be tested at gravitational wave detectors.

The String Theorists are pretty much going to be on the back foot until they put up something that says this is not just the standard model or x model this is discrete because x doesn't have this or this.

See above

There is a theory that has become strong enough its called the standard model which predicts the missing Higgs. It is the mainstream. Your proto theory is still at the planning stage now you have to test it.

The Higgs mechanism is not a main feature of the standard model. Spontaneous symmetry breaking is explained by a number of theories, including Technicolor theories.
Spontaneous symmetry breaking has never been tested. This is the very flaw that you use to criticize string theory, yet you clearly disregard it here. Please be coherent.

[Nautilidae]

Anything interesting yet?

Well, there have been several interesting papers. For instance, according to one of the talks, when one applies Chern-Simons theory to electromagnetic fields surrounding a black hole in AdS space, energies turn out to be much higher than expected. There were also several papers on new F-theory compactifications.

I'm particularly interested in whether one can get the Standard Model out of string theory. There are three possibilities:

1. It is not possible to get the Standard Model out of string theory.
2. It is possible to get the Standard Model out of string theory, but also lots of similar theories resulting from different space-time topologies and boundary conditions.
3. It is possible to get the Standard Model out of string theory, but no similar theory.

The impression I get is that string theory partially fits case 2, with little progress toward demonstrating or rejecting either case 1 or case 3. Is that a fair statement?

Yes, it is. String theory can produce the standard model, but it can also produce a number of other situations as well.

I think that we will be in a better position when the LHC has run for a while. We will either see particles predicted by supersymmetric extensions of the Standard Model, or else we will push lower limits up by at least a factor of 3. Either possibility will help improve constraints on GUT-scale physics and make possibilities 1 and 3 more testable.

This.

[JimC]

Hackenslash wrote:

JimC wrote:
Although you could really call it a speculative model, containing a whole heap of hypotheses and an intricate web of mathematical reasoning that few can grasp in its entirety...

No argument here.

I'm not really against it, just waiting for it to generate experimentally testable predictions, whether via cosmological data, or high energy particle physics.

It has made testable predictions. I often come across people not making the connection between Turok and Steinhardt's 'brane-worlds' model (not suggesting that this is the case here), but that model is rooted in M-Theory, and it has made testable predictions, which I will come to.

I guess I should have said that I am really waiting for those testable predictions to actually be tested... Until then, whether we call it a weak theory (with much interesting internal scaffolding) or a series of hypotheses is a moot point. I certainly put it aquarely within the realm of science, given that it can, in principle, be tested. I suspect the sticking point for many is that it has been in existence for a long time, and most of the developments revolve around the increasingly intricate mathematics, which makes it rather different from many other areas of physics, where the theory and the experimental data were much more closely linked in time.

Looking forward to seeing how it copes with real data, when the technology reaches that point.

[Nautilidae]

I guess I should have said that I am really waiting for those testable predictions to actually be tested... Until then, whether we call it a weak theory (with much interesting internal scaffolding) or a series of hypotheses is a moot point. I certainly put it aquarely within the realm of science, given that it can, in principle, be tested. I suspect the sticking point for many is that it has been in existence for a long time, and most of the developments revolve around the increasingly intricate mathematics, which makes it rather different from many other areas of physics, where the theory and the experimental data were much more closely linked in time.

What a lot of people don't realize is that the tests for string theory rely on very high energy experiments. Other than a few exceptions, this hasn't been possible until the past few decades.

Looking forward to seeing how it copes with real data, when the technology reaches that point.

[Gawdzilla Sama]

[The Dagda]

I guess I should have said that I am really waiting for those testable predictions to actually be tested... Until then, whether we call it a weak theory (with much interesting internal scaffolding) or a series of hypotheses is a moot point. I certainly put it aquarely within the realm of science, given that it can, in principle, be tested. I suspect the sticking point for many is that it has been in existence for a long time, and most of the developments revolve around the increasingly intricate mathematics, which makes it rather different from many other areas of physics, where the theory and the experimental data were much more closely linked in time.

What a lot of people don't realize is that the tests for string theory rely on very high energy experiments. Other than a few exceptions, this hasn't been possible until the past few decades.

Looking forward to seeing how it copes with real data, when the technology reaches that point.

What few people realise is this hasn't been possible isn't now, and probably never will be. String theory is piggy backing other theories it has nothing of its own.

Some people need to read Not Even Wrong, The Trouble With Physics or Smolins blog which explains in detail while CERN cannot turn up evidence of strings and no one believes it will in mainstream physics. Once again you are the victim of the same propaganda machine that demeans science.

Once upon a time, physicists were taking every opportunity to promote string theory as a "theory of everything." In this book, Smolin dramatically argues that string theory has failed at this goal. String theory is a useful theory but certainly not one which describes reality at a fundamental level, and he proposes searching elsewhere for a more fundamental theory.

At the center of his argument is the idea that string theory does not determine physical parameters, but allows for a vast "string theory landscape" (a phrase by string theory founder Leonard Susskind) which requires measurement of various parameters to match our universe. A fundamental theory, Smolin argues, would tell us why the universe has the parameters it does, rather than making us measure them.

Even more significant than his specific criticisms of string theory as science is his criticism of scientific research as a whole. He accuses academia of containing inherent prejudices which inhibit the introduction of new talent - especially minorities and women - into the field, and which punish new ideas and promote the status quo. String theory, as a dominant theory which has produced little, is used to present this case, but the case itself is more dramatic. In part due to string theory, Smolin feels as if the last generation of theoretical physicists - his generation - has left no lasting legacy, instead having squandered their talents on exploring string theory instead of looking into new areas.

These new areas include topics such as loop quantum gravity, deformed special relativity, modified gravity (MOG), variable speed of light (VSL), and other less-researched areas. As Smolin sees it, the emphasis on string theory has unfairly forced these theories into the background ... and he makes a strong case.

http://physics.about.com/od/stringtheor ... hysics.htm

[The Dagda]

Anything interesting yet?

Well, there have been several interesting papers. For instance, according to one of the talks, when one applies Chern-Simons theory to electromagnetic fields surrounding a black hole in AdS space, energies turn out to be much higher than expected. There were also several papers on new F-theory compactifications.

I'm particularly interested in whether one can get the Standard Model out of string theory. There are three possibilities:

1. It is not possible to get the Standard Model out of string theory.
2. It is possible to get the Standard Model out of string theory, but also lots of similar theories resulting from different space-time topologies and boundary conditions.
3. It is possible to get the Standard Model out of string theory, but no similar theory.

The impression I get is that string theory partially fits case 2, with little progress toward demonstrating or rejecting either case 1 or case 3. Is that a fair statement?

Yes, it is. String theory can produce the standard model, but it can also produce a number of other situations as well.

I think that we will be in a better position when the LHC has run for a while. We will either see particles predicted by supersymmetric extensions of the Standard Model, or else we will push lower limits up by at least a factor of 3. Either possibility will help improve constraints on GUT-scale physics and make possibilities 1 and 3 more testable.

This.

That's because String Theory is a theory of anything, and cannot be disproven, but anyone wanting to discuss this would best be served going here, so as not to derail this thread.

3.It is possible to get the Standard Model out of string theory, but no similar theory.

Except Loop Quantum Gravity (LQG) and many others but why let that trouble you?