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B Is supersymmetry dead?

  1. Feb 21, 2018 #61
    When I described that physics tried to treat different objects (particles) in isolation. It's not in the context of unifying all in one TOE. I'll give you an example. When you study a human body in isolation. You detect the water molecules, the ligands, the mitochrondria or let's make the scale even smaller.. you detect the atoms in the body like oxygen, carbon, hydrogen, etc. Here you may not detect anything new. But when you view the entire body at once. There may be emergent properties (new physics) you can't detect individually.. what is the term for this macroscopic properties (maybe this is the term?)?

  2. Feb 21, 2018 #62
    Yes, I will pay attention to this book.
    My main problem with string theory is that it does not make testable predictions at low, high or extremely high energies only produces more and more theoretical possibilities of different exotic vacua.
    Not long ago we had 10^500 different possibilities, later 10^520 of them.
    However there was significant progress made (which I was unaware of until yesterday) and now I have found that we have 10^272000 different possibilities.
    This is an insane number and of course 10^500 was also insane.
    We are heading for major problems with string theory, namely it is more and more challenging to write a number of discreet vacua possibilities on a page of paper.
    Usual exponential notation is hitting its limits. Perhaps tetrations and Knuth notation will come to rescue.
    Good news are that theory might be falsifiable after all.
    All what we need to do is to prove that number of discreet vacua possibilities is actually infinite and our low energy world came from one of infinite number of high energy worlds and it have arrived by one of infinite number of possible paths (or maybe by all of them at the same time).
    At this point theory will be *renormalized*, eg discarded in its entirety and work will be directed into some other, more promising areas.

    Major problem with string theory is one of *pride*. Pride of very bright peoples preventing them from admitting that they have been wrong.
  3. Feb 21, 2018 #63
    Kane book has addressed the above.. in fact, the following passage is one of those I highlighted (it has address all my concerns which finally made me understand the field a bit better):

    "If we want to test a theory of our world we have to find it and calculate its predictions. This is another issue where much that is said is confused. People talk of very large numbers of solutions of string theories, and claim will be difficult to find one that could describe our world among the huge number. In fact, compactified theories generically have many realistic features whose presence limits the number of possible theories. These features include gravity, Yang-Mills forces like the Standard Model ones, chiral quarks, and leptons that give parity violation, softly broken supersymmetry, Higgs physics, families, hierarchical fermion masses, neutrinos, inflaton candidates, a solution of the hierarchy problem, a solution of the strong CP problem, and more. Solutions with such properties are easy to find. There is still work to do to calculate sharp testable predictions and compare compactifications, but a reasonable amount of work is already done."

    About your 10^272000 different possibilities. I think the shape of the Calabi-yau manifolds is programmed that way by some moduli dynamics. I mean.. there may be some more fundamental theory than superstring theory.. and these could be give the input or parameters to the Calabi-yau manifolds. This makes better sense.
  4. Feb 21, 2018 #64

    Urs Schreiber

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    Anyone who thinks that string theory has more solutions than usual for a physical theory, I invite to determine the number of solutions of these usual theories.


    Consider usual Einstein-Yang-Mills-Dirac theory .


    FIx a semi-realistic gauge group and fermion content.

    1) Does the theory have a finite number of solutions?

    2) If not, does it have at least a finite-dimensional continuum of solutions?

    3) If not, in which sense is the space of solutions smaller than the finite number ##10^{500}##? If it is?


    For better comparison with string theory, consider this question without fixing the gauge group and matter content. Hence consider the union of the spaces of solutions found in (I) as the choice of gauge group and matter content varies.

    Can you get any handle on the size of the resulting "landscape" of solutions to usual Einstein-Yang-Mills-Dirac theory?
    Last edited: Feb 21, 2018
  5. Feb 21, 2018 #65
    I will have to do some homework to make any intelligent comments on it.
    All I may say at the moment is that quantum field theories dealing with low energy physics have a comfort to refer to experiment for verification of outcomes and string theories does not enjoy it.
    I suspect that from initial 10^272000 of possible string theories we are going to get maybe 10^271500 and probably more possibilities which are going to give low energy world like we know.
    So which one should we choose? First come, first served?
    Mind you, with current peace of expansion of possibilities we may soon get to 10^^272000 possibilities. What then?
    What would be for you a trigger to give up?

    "...There may be some more fundamental theory than string theory"
    But any experimental evidence for it will be hidden under event horizons, somewhere at 10^400 GeV or so.
    We won't get anywhere by "Russian doll theory" approach.
  6. Feb 21, 2018 #66


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    The money...
  7. Feb 21, 2018 #67

    Urs Schreiber

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    Try to focus on one thought at a time, not jumping randomly around the supply of woitianisms.

    Let's agree that string theory is all wrong, so that you can focus just on the logic, not getting distracted by the sports competition spirit. What I would like you to do is understand just the logical fact, in itself, that it is rare in physics that a theory admits a finite number of solutions, and to understand the fallacy of thinking that any finite number, immense as it may seem, can be larger than the cardinality of the continuum.
  8. Feb 21, 2018 #68
    Martin0001, can you read this free preface of the book "String Theory and the Real World" now.. https://www.amazon.com/String-Theor...8-1&keywords=string+theory+and+the+real+world

    then if you can't get it elsewhere.. buy the kindle version... it's only a 2 hours read the entire book.

    I don't know your background. It's to have baseline and being updated of the latest. Then instead of criticizing Woit (whose stuff is more than a decade old). Try to critique Gordon's instead. I'll share some passage to get you going:

    "Many experts who specialize in various aspects of string theory will not endorse the possibility that the final theory of our vacuum may be soon forthcoming, because they work in technical areas that lack overviews. Anyone who focuses on solutions in other than four dimensions, or black hole solutions, or anti-de Sitter space/CFT, or amplitudes, or moonshine, or many other areas will have no reason to expect a comprehensive theory to emerge. And of course solutions can be constructed that do not describe our vacuum. Similarly, experts in QCD physics or Large Hadron Collider (LHC) physics or dark matter physics will not have an overview of the ingredients described below, and generally will not be aware of the emerging final theory opportunity, Some who are not aware of it will be skeptical of it."

    "Much has been written about the testability of string theories - we will see that compactified string/M-theory are indeed testable in the traditional way of physics theories, contrary to what is being said and written in a number of journalistic articles, blogs, and books"

    Read the whole book now and please critique it. Thanks.
  9. Feb 22, 2018 #69
    I have red free introduction. To say something of value I need to read entire book (will buy it and it will take some time to get - I live in Poland).

    Nevertheless what I have found in introduction is already troublesome.

    Author has a great hope that LHC will turn some evidence of dark matter particles and SUSY (book was published in 2017 and written probably earlier).
    He acknowledges need to feel gaps in understanding of DM and SUSY, explicitly electroweak SUSY.
    As we already know electroweak SUSY is rather out of question - it is not there according to LHC results.
    DM particles are not detected either.
    LHC results are pointing towards so called Great Desert - very bad scenario for those hoping to support BSM models by experimental evidence, btw possibility of such an outcome is acknowledged.

    He is mentioning 2 successful theories upon which some unified theory could be built.
    First is Standart Model of particle physics, second is Standart Model of cosmology.
    With first I do not have any problem - it is very successful.
    Second is a domain of speculations. Inflationary models of early Universe are heavily criticised by many prominent scientists, including those initially heavily involved in work on them (Steinhardt).
    Inflationary models are not resolving hurdles they were meant to address, eg fine tuned initial conditions.
    It have been shown that for fine tuning to be addressed by inflation, initial pre-inflation conditions would have to be even more fine tuned than without any inflation at all (Penrose).
    On experimental front protons are still refusing to decay very much like sparticles are refusing to turn up.
    Inflation is mainly kept alive to let peoples talk about someting (beginning of Universe) even if actually they really don't know what they are talking about (as quantum theory of gravity is elusive) (Hossenfelder).
    So at the moment I am not convinced that inflation based cosmology has a status of well supported theory. It is rather based on faith and wishful thinking (and yes, I am aware of results related to uniform CMB and flatness issue).

    Finaly I observe that author is strongly convinced about possibility of unification of gravity with other forces.
    What if Nature have decided the other way?

    Of course to say anything more I would need to read whole book, not just an introduction.

    I do not criticize Woit. I agree with him. If you think that I criticize Woit then show me where.

    Yes I understand your argument about large numbers and continuum.
    The issue which Woit is rising is not only about large numbers of possible theories.
    In QFT regarless of large numbers of possibilities some *simplest* assumptions related to gauge symmetry delivered a working theory. This is not true with string theories.
    For example we have a continuum of numbers.
    Ever wondered why numbers like 1,2 or 3 are somehow more useful in maths (or at least more often are turning in various equations describing Nature) than lets say number 5744869447463274733?
    Nominally they are all equal after all.
    QFT relies on simplicity of initial conditions to work and string theories are relying on large numbers from which something (hopefully) can be fished out.
    He is also claiming that to make any variant of string theory resembling anything real one would need to put more and more information in and develope increasingly complex Calabi - Yau manufolds.
    His point is that string theories are information neutral. You do not get out of string theory any more information about Universe than you put in.
    Hence they are not useful.
    It is not my intention to criticise your work or whatever. String theories have led to great developments in maths and yes there are some spinoffs helping in down to Earth physics. They do have practical applications.
    However there are indications that these theories are unlikely to explain workings of Universe.
    Don't you think that Multiverse ideas are subtle admissions of defeat?
    Last edited: Feb 22, 2018
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