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Should top Universities engage in nonstring QG research

  1. Mar 29, 2017 #1
    many of the top universities like Princeton, Harvard, MIT, Stanford have a string theory research group and only string theory for QG. in light of non-susy @ lhc, no proton decay, no dark matter discovered no extra dimensions,

    is it now time for top universities like Princeton, Harvard, MIT, Stanford have a string theory research group to also sponsor a non-string QG research such as LQG, LQC, AS, NCG, twistor CDT?

    QG remains an outstanding unsolved problem in physics, and nonstring QG faculty, research, grad students is absent at these top schools.

    Penn state university is famous for having Abhay Ahsketar and a LQG/LQC faculty, grad students, they hand out phD's in LQG.

    AFAIK, Penn state is the only university in the US that has this. there is one-two LQG Pullin is at LSU and John Baez is at SoCal. Princeton is famous for having Witten and several other string theorists on faculty, and they award phD's and grad students in string theory.

    Should Harvard, Princeton, Stanford, MIT, Berkley, Carnegie Mellon, which all have string theory researchers, also have a LQG/AS faculty analogous to Penn state?

    LHC found NO evidence of SUSY or extra dimensions so it seems it's time for top physics departments to fund nonstring QG research to be fully supported.

    does it make sense for the top universities that have string theory research groups to continue to sponsor string theory and only string theory to the exclusion of alternatives QG like LQG, AS, which do not require SUSY or extra dimensions, when the LHC has found no evidence for SUSY, Dark matter, or extra dimensions?

    not finding any hints of susy @ lhc after 36 fb-1 means it is unlikely LHC will find susy

    china has expressed interest in building a 100km 100 tev collider $20 billion with timeline of 2040-50
    and it may not find susy either

    should string theory and only string theory be the primary QG research by top universities physics departments all to 2050 and beyond, even if a 100tev collider finds no evidence of susy, extra dimensions or dark matter or any hints of BSM?

    sabine hossfelder bee was asked this and she said no, top physics research centers should not sponsor LQG/LQC research. i don't understand why it is a problem for princeton, harvard, stanford rutgers to have a LQG/LQC research group similar to penn state, or perhaps penn state's LQG should be shut down and abhay ashketar fired from his job and replaced with lubos motl.
    Last edited: Mar 29, 2017
  2. jcsd
  3. Mar 30, 2017 #2


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    What sort of answer do you wish to hear? People have answered you several times but it appears you don't like the responses.

    At the end of the day the type of researchers a university hires is typically made at the highest levels and are done by search committees that are aiming to achieve specific criteria that are established in advance. It's important to note these criteria differ between institutions quite dramatically depending on whom they already have on staff, funding and expectations for the future.

    A smaller university that feels it can't compete with a large, well funded institution like Harvard might opt to achieve a monopoly in a far less mainstream and riskier research direction (like LQG) with potentially large payoffs. Yet other universities will try to go for a bit of everything.

    In any event, this doesn't answer the 'should we' question which is another matter, and gets into the very old, thoroughly well documented strings vs lqg war that you can find discussed in the blogosphere elsewhere. Nothing has really changed one way or the other so everything that was said before continues to apply.
  4. Mar 31, 2017 #3


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    If you want to study LQG, or collide particles, or explore non-oil energy, leave USA and go to Europe. :biggrin:
  5. Mar 31, 2017 #4
    thanks i've always wondered about how universities decide this

    in light of recent LHC results of 36 fb-1@13tev of no SUSY + no proton decay + extra dimensions + no dark matter detected, doesn't that constitute a change?

    should this specific criteria change in light of new experimental null results?

    Since Harvard, Princeton, Stanford, Berkley MIT Rutgers Carnegie Mellon Univ of Chicago selection criteria is to have a world class physics department, with world class physics research, and to be a leader in physics, to be at the cutting edge of physics, including quantum gravity

    they all have string theory research group, why not, at this time, in light of recent null results for SUSY, also add LQG, asymptotic safe gravity, emergent gravity etc

    these top universities all offer both undergraduate and graduate level courses in string theroy to undergraduates and graduates
    should these top universities also offer LQG/LQC, asymptotic safe gravity, emergent gravity etc for undergraduates?
  6. Mar 31, 2017 #5
    In the history of research on gravity, you have work on classical topics like black holes and gravitational waves. Then perhaps the two pivotal concepts in the beginning of quantum gravity, are Feynman's treatment of the metric as just another quantum field - giving you the graviton; and Wheeler's wavefunction of the universe, leading e.g. to Hawking's quantum cosmology.

    There is "nonstring QG research" which is continuing these older lines of research. For example, Andrew Strominger hasn't done any string research for about a decade, that I can see. It's all been symmetries of black holes and "soft graviton theorems". Or another current topic, which falls in the category of gravity as just another quantum field, would be "double copy relations" between gauge theory amplitudes and graviton amplitudes. The study of gravity as a quantum field is a living topic with applications (see John Donoghue), and that is technically "nonstring QG research".

    However, I think it's true that one can draw a rough dividing line between nonstring QG research which is string-compatible, and that which is not. The "classic" topics that I mentioned, and their contemporary continuations, are string-compatible because they are based on general relativity, and general relativity is the field-theoretic limit of stringy gravity.

    A lot of what you are calling for (though maybe not all of it) seems to be in the category of "not compatible with strings". For example, if you want to treat Feynman's field-theoretic quantum gravity as the final theory, you appear to have a problem of predictivity - infinitely many parameters (different couplings for arbitrary numbers of gravitons meeting at a point). String theory solves that by replacing particles with strings and Feynman diagrams with string diagrams, in which only one coupling constant is needed. Asymptotic safety wants to solve the problem by demonstrating the existence of a finite-dimensional attractor in the "running" (RG flow) of those infinitely many parameters.

    There are other field theories of gravity, apart from general relativity, which seem to be string-compatible. Conformal gravity is one (but not all work on conformal gravity is string-compatible, e.g. Phillip Mannheim). I am not sure about topologically massive gravity, but I see very mainstream theorists working on it, so I think it must be. On the other hand - again judging just by who does the research - I think unimodular gravity might be "not string-compatible".

    Verlinde's emergent gravity is a borderline case; it was inspired by string theory, but it doesn't seem to be compatible with string theory any more, but it hasn't reached its final form yet. Twistors are a special case, basically an unusual approach to quantum field theory including quantum gravity, that ended up being highly string-compatible in certain forms. Noncommutative geometry is a similar story, there are parts of NCG that are within string theory and parts that are not.

    To understand the appeal of string theory you also have to remember that it's not just a theory of gravity, it's also a theory of everything else. It was particle physicists using quantum field theory who decided that grand unification and supersymmetry are probably true, and those things are also found in string theory. But string theory is obliging in this regard, and if particle physicists do abandon those topics, the string phenomenologists will be able to follow suit.

    So if you want a nonstringy quantum gravity to be part of a total theory, it has to be coupled to other quantum fields. And of course many of the other QG research programs investigate this: NCG, asymptotic safety. One thing that string theory can do in principle, that is not so easy for a field theory, is to explain the values of coupling constants (e.g. as deriving from the volumes of branes) and particle masses (e.g. as deriving from surface areas of string interaction vertices). In a field theory, if those quantities are not to be arbitrary, you need other mechanisms like RG fixed points (as with Higgs mass from asymptotic safety) or perhaps discrete symmetries (see the study of neutrino "textures").
  7. Mar 31, 2017 #6
    there are Loop quantum gravity papers on ads/cft
    Loop Quantum Cosmology makes some empirical contact with inflation.

    AFAIK, physics prodigy Jacob Barnett is at PI studying Loop quantum gravity under Lee Smolin.

    regardless of whether Loop quantum gravity is "not compatible with strings" is there a good reason for Princeton not offer Jacob Barnett an academic research position in Loop quantum gravity provided Barnett produces quality LQG research? as well as undergraduates interested in LQG

    to put it another way, by definition of a top physics university research department, whose mission is cutting edge physics in QG, who have string theory researchers like Princeton, Stanford, Harvard, MIT, shouldn't they have Loop quantum gravity researchers on faculty?

    some teenage physics prodigies like Jacob Barnett are interested in QG specifically LQG. shouldn't top physics universities offer courses in LQG for those students interested?
  8. Mar 31, 2017 #7
    What research is done by physicists is up to the physicists themselves, based on their own judgment. You should be aware that people at places like Harvard, Princeton etc don't consider LQG to be "cutting edge physics in QG", so they are unlikely to hire colleagues who work in that area.

    Finding supersymmetry at the LHC was never a necessity in string theory, so it doesn't change anything.
  9. Mar 31, 2017 #8
    this could be an error in judgment. if SUSY doesn't explain the naturalness problem, it is no longer well motivated. SUSY may not be a fundamental symmetry in nature nor GUT nor extra dimensions.

    Should places like Harvard, Princeton hire colleagues who based on their own judgment want to research LQG, whose graduate thesis and dissertation work was based on LQG, and meet acceptable qualifications?
  10. Apr 1, 2017 #9

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    This is true.

    This is also true. But see above.

    The idea that universities should make multiple 30-year appointments to accommodate "teenage physics prodigies" is ... well, there are so many possible adjectives it's hard to pick just one. Let's just go with "unrealistic".
  11. Apr 1, 2017 #10
    would you feel differently if Jacob Barnett was studying string theory at Princeton under Witten, and seeking an academic position?
  12. Apr 1, 2017 #11

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    If Jacob Barnett wanted to study LQG, I would expect him to go somewhere that had a good LQG program. I would not expect some other university to set one up just for him.
  13. Apr 1, 2017 #12
    I never suggested some other university to set one up just for him

    this is Jacob Barnett's bio

    Jacob Barnett is an 18-year-old theoretical physicist at Perimeter Institute. His research areas are loop quantum gravity and quantum foundations. He boasts an IQ of 170, that is believed to be higher than Albert Einstein.

    his phD advisor is Lee Smolin

    would you have any problems with him seeking a full faculty research position at a top physics department like Princeton, Harvard, Stanford MIT?
  14. Apr 1, 2017 #13

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    I have no idea what you are talking about if you're not talking about opening faculty positions for non-string QG research in a thread titled "Should top Universities engage in nonstring QG research"
  15. Apr 1, 2017 #14
    I do think top universities should open faculty positions for non-string QG researchers, but not specifically teenage prodigies like Jacob Barnett which is what you seem to imply when you said

    Jacob Barnett is just an example of someone earning a phD in LQG, non-string QG.not to specifically accommodate a teenage prodigy for multiple 30 year appointments but simply bc he is qualified and nonstring QG is worthwhile research that a top university physics department should research in.
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