Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Poplawski's Paper on Invalidity of Superstring Theory

  1. Sep 27, 2012 #1
    Gravity with spin excludes fermionic strings
    The existence of intrinsic spin of matter requires the metric-affine formulation of gravity, in which the affine connection is not constrained to be symmetric and its antisymmetric part (torsion tensor) is a dynamical variable. We show that the cyclic identity for the curvature tensor in the metric-affine formulation forbids fermions represented by Dirac spinors to form point or string configurations. Consequently, fermionic strings contradict the gravitational field equations in the presence of spin. Superstring theory is therefore incorrect.

    From Page 7:
    Superstring theory, or supersymmetric string theory, assumes that all elementary fermions are oscillating, one-dimensional strings whose length is on the order of the Planck length. Although that theory lacks predictive power, it has become the most popular contender for a theory of everything. The results of this paper show that one-dimensional fermionic strings contradict the cyclic identity for the curvature tensor in the metric-affineformulation of gravity which is required in the presence of intrinsic spin. In addition, the simplest (ECSK) gravity withspin requires fermions to be spatially extended on the order of their Cartan lengths which are much greater than the Planck length. Consequently, fermionic strings contradict two combined physical phenomena that are well-established by experiment and observation: the geometric nature of the gravitational field and the existence of spin. Fermionic strings are thus unphysical and superstring theory is incorrect.
  2. jcsd
  3. Sep 28, 2012 #2


    User Avatar
    Science Advisor

    Is this widely accepted as fact in quantum gravity programs such as LQG and string theory? It certainly isn't embraced widely in general relativity.
  4. Sep 28, 2012 #3


    User Avatar
    Science Advisor

    I think it is accepted in LQG:
    but not in string theory.
  5. Sep 28, 2012 #4
    In supergravity the affine connection is not required to be symmetric and the torsion part is allowed. I believe this was first shown to be possible by Cartan but I could be wrong.

    The problem with this paper is that it looks like everything is done classically so I don't think it really has any bearing on actual string theory. You can't use just classical identities and classical fields to try and disprove quantum theories. I haven't read the whole thing and feel free to correct if I'm wrong.
  6. Sep 28, 2012 #5


    User Avatar
    Science Advisor

    This is not true.

    Yes, the antisymmetric part is related to torsion, but torsion is NOT a dynamical variable in Einstein-Cartan-Theory.

    Torsion can expressed algebraically in terms of matter d.o.f. = spin currents; therefore torsion vanishes in vacuum (where the matter spoin current vanishes); and torsion is non-propagating, i.e. there are no torsion waves, so torsion is always confined to non-vacuum regions.

    I don't know whether there are extensions to Einstein-Cartan with dynamical torsion, but within Einstein-Cartan torsion is not a new d.o.f.
  7. Sep 30, 2012 #6
    At a fundamental level: very interesting. From my viewpoint as amateur this kind of paper looks like a "bomb". It will certainly save hours of unnecessary work and it also clarifies the situation. My unique question after having read it is: why don`t we need cosmic inflation in that theory (ref. [10])?

  8. Sep 30, 2012 #7
    Or, string theory is correct and we may have to modify gravity again.
  9. Sep 30, 2012 #8
    Or, just judging by the references one can tell immediately that this is not a serious paper.
  10. Sep 30, 2012 #9
    Do you mean calculations are wrong? (I didn't check them and my lecture was concentring on the understanding of the essence of that paper). Or dou you disagree with the conclusions and have well-founded rationalistic reasons for that conclusion that you would be ready to explain here?
  11. Sep 30, 2012 #10


    User Avatar
    Science Advisor
    Homework Helper

    Can you comment on the references ? Why would you think it's not serious ? What sources are missing or which are wrong ?
    Last edited: Sep 30, 2012
  12. Sep 30, 2012 #11


    User Avatar
    Science Advisor

    I think what the paper shows is that a certain classical delta-function-like string-like excitation is incompatible with Einstein-Cartan theory; I don't know whether this is a classical limit of string theory
  13. Sep 30, 2012 #12


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    I just want to note that three days ago (27 Sept) Peter Woit dismissed the Poplawski paper as "nonsense".

    ==quote Woit in reference to http://arxiv.org/abs/1209.5772 ==

    The claims about superstring theory in that paper are nonsense. The paper is purely about classical physics, and the “string-like” classical field configurations discussed in it have nothing to do with quantum superstring theory, whatever it might actually be.

  14. Sep 30, 2012 #13
    If you go around making claims much bigger than your reputation calls for, you should at least make your paper look credible, and pass the first "garbage test" most serious people use.

    Point is, papers like this come out every other day. My email is spammed every other week by some random guy asking me whether his new theory of everything including spaghetti is correct. No, I take that back, not asking whether it's correct, but demanding I take notice of it.

    I assume known people in the field have it much worse. That's why you make this garbage filter: paper comes from unknown guy, from unknown place, with huge claim. Ok fine, let's take a first look: does his paper have any actual equations? Next, so ok he claims something is very wrong with s.t. Ok fine, does he seem to at least acknowledge (even if by a random couple of references) the previous work done in the field, and maybe comment on how it was wrong, what was overlooked, and basically try to convince me why I should read through his paper, which goes against the work over 40 years of some very capable people? Oh, he only cites "the elegant universe" as his source of information on string theory? And then Smolin?

    Then half of the other references are his own papers and various textbooks?

    Yeah that's a good point to conclude you just wasted 1 minute of your life by skimming over the paper and that it demands no further attention.
  15. Sep 30, 2012 #14


    User Avatar
    Science Advisor
    Homework Helper

    I see your point. It's indeed quite abnormal to make assessments about results of a theory you have not contributed to. You don't need a rebuttal paper to dismiss it.
  16. Sep 30, 2012 #15
    Making contributions is already way too much. I would've been happy if there was at least some indication the guy actually read anything on string theory besides the elegant universe. Citing some more relevant works is a good way of showing you might actually know some things about the field.

    -(or given the size of the field, no citations at all would have been better - citing work for well know results is just as bad. this is why if someone formally cites einstein for e=mc^2 you can again just go ahead and ignore the paper)

    This method of course is just a statistical filter. You might miss otherwise valuable papers. But the chances for this are pretty low. I just find it highly unlikely that some random guy, lacking deep knowledge of a field, can find some trivial argument disproving string theory, which someone like witten or 20 other big shots completely missed. Things like this just never happen.
  17. Sep 30, 2012 #16


    User Avatar
    Science Advisor

    You should give such nonsense more chances - since you have just wasted 2 minutes of your life explaining why it is nonsense on PF :tongue:
  18. Oct 1, 2012 #17


    User Avatar
    Science Advisor

    As Negru says, this is a good sociological indication on how physicists sort through papers.

    The claim not only invalidates string theory, it also claims to rule out all fermionic point particles in GR as well (hence invalidating most of physics). Almost the entire paper consists of equations and text you will find in any introductory textbook.. Except for one equation. Not surprisingly, the one equation is wrong (i'm not going to list what it is, b/c these types of authors typically read the internet and will actively engage you in a time wasting marathon)!

    As a general rule, in any suitably advanced and aged subject (like GR, or QFT or string theory) you probably are not going to find any simple 'flaw' in the reasoning. There are too many good physicists, postdocs, grad students and undergrads who have checked, rechecked and gone over the mathematics in dozens of different idiosyncratic and independant ways.

    If you are going to find a flaw, it will almost always be something very subtle.. Something like black hole firewalls (an example of recent controversy in theoretical physics which is far from obvious)

    Not that you shouldn't go through things from first principles, far from it, its just that you probably shouldn't publish until you have consulted suitable experts.
  19. Oct 1, 2012 #18


    User Avatar
    Science Advisor

    I think the problem is due to an incorrect treatment of delta functions. The first problem is to use a delta-function-like eneregy-momentum tensor which should be bilinear in the fermion fields. This ansatz is very obscure.

    As I said, the paper only shows that this specific ansatz is incorrect.
  20. Oct 1, 2012 #19


    User Avatar
    Science Advisor

    That tells enough about the value of the paper.
  21. May 10, 2013 #20
    Hello, I bring up this old topic cause I wanted to react/ask something about what negru said.
    It sounds very logic and rational and I could agree but I have objections and will provide an actual example this is not exactly true, or an example this is only unlikely, because it happened once.
    First my objections are: people don't check again and again the basis of a theory. The older it is and the more complex it is, the less someone serious dares to disprove anything accepted, except crackpots whom are not heard. Even if you are among the smartest people in the world, you can not think about everything. More precisely a "more" complex theory is also more complex for a smart guy, that means you increase the probability than even smart ones don't find anything suspicious whether or not there is a flaw in the theory. This is the very reason man believed (and still believe) in anything but real science for thousands of years, conformism and the possibility to be wrong in front of the others. The science community is not immune of beliefs and conformism, this is my belief. You can also add the fact the average student just don't have the time to think about all what he learns, and imagine all possibilities, I hope you agree. There are plenty room to check what has already been studied. If there wasn't research would be end now, and we would have find the "final theory".

    So my example now, more concrete, and there are others, is the case of what is called "hidden momentum", which was enlightened by David Babson a student. Hidden momentum concerns electromagnetism, so if you read the story of David Babson, you will discover very few people among you thought deeply about the basis of what they were learning.

    An other example is dictated simply by the theory we are talking about, LQG and Strings are very different theories, let's say, even if not true, the LQG and Strings are considered to be both as plausible by the scientific community. If one is one day considered "true",(not talking about the meaning of truth), the other is wrong, which also means something, may be as basic as the premises of the theory is wrong, and that very smart people worked on it for 40 years without noticing it.

    There are so big divergences between the two theories, it's hard to believe only subtle points can distinguish them. They are very different, and nobody can prove what is postulated in the theory.

    I hope you enjoyed my dirty English, I am French, so please forgive me for the strange construction of sentences and the lack of vocabulary.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook