Quick Post

I’m traveling this week, so I don’t have time for a long post. I am rather annoyed with Sabine Hossenfelder’s recent post about string theory, but I don’t have time to write much about it now.

(Broadly speaking, she dismisses string theory’s success in investigating quantum field theories as irrelevant to string theory’s dominance, but as far as I’ve seen the only part of string theory that has any “institutional dominance” at all is the “investigating quantum field theories” part, while string theorists who spend their time making statements about the real world are roughly as “marginalized” as non-string quantum gravity theorists. But I ought to gather some numbers before I really commit to arguing this.)

6 thoughts on “Quick Post

  1. Sam Homiller

    Someone was asking me about this article the other day and I had almost the same reaction. One thing I’m curious about though – is this “history” of string theory repeatedly running into a catastrophic issue, then being tuned or modified to avert it (the author points to, for example, extra dimensions, positive cosmological constant) really true? My impression was that these were never seen as fundamental flaws to begin with – particularly requiring extra dimensions.


    1. 4gravitonsandagradstudent Post author

      Yeah, she’s stretching things for dramatic effect. Extra dimensions just wasn’t seen as a flaw, since people already knew how to compactify. Of the “tunings” she mentions, most aren’t modifications of the theory, but rather people figuring out how the theory can give rise to something. R-symmetry isn’t even that, really: if you’re starting from low-energy SUSY then R-symmetry is ad-hoc, but from a string perspective it’s just the default thing that happens when you compactify, and you pretty much have to go out of your way to avoid it.

      Liked by 1 person

  2. Giotis

    When you say “real world” I presume you have in mind String phenomenology, otherwise every aspect of String theory is referring to the real world. The theory is one, either you see it as a theory of Quantum Gravity or a theory of everything or a Swiss army knife for studying various QFTs.

    As for her post, is truly ludicrous, full of misconceptions and pompous uneducated absurdities.

    I think she is deliberately being provocative though; she is in an anti string frenzy for some time now maybe because she is writing a new book and needs the attention to promote it☺

    Liked by 1 person

    1. 4gravitonsandagradstudent Post author

      I’m referring to string phenomenology, and a few similar fields (string cosmology, some of the black hole microstates people). While string theory is a theory of the real world, most of what people do with string theory involves statements about configurations that the real world doesn’t happen to be in. For example, N=4 super Yang-Mills is a low-energy limit of string theory, but not of our vacuum.

      I agree that she’s being intentionally provocative, though I’m not quite so cynical about the reason. She’s venting, and she pretty explicitly labeled it as such (“how a cynical outsider might tell this story”). Venting generally isn’t careful, or charitable to the other side. It’s just not the genre.


      1. Giotis

        Yes but people study such theories to understand aspects of the real world; in this case QFTs at conformal or Supercomformal fixed points, RG flows, pure QCD and so on.

        6d (2,0) SCFT seems so exotic at first but it is intensively studied not only because it describes the low energy dynamics of M5 branes but because it can be used to provide, among other things, a deep understanding of electromagnetic duality in four dimensions.

        That is why String theory is so amazing after all; it is at the center of a highly non trivial web of interconnected physical ideas and notions weaving the fabric of Nature at the most fundamental level.

        Liked by 1 person


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