Prospects and Limits For the LHC's Capabilities To Test String Theory

StartsWithABang writes: The Large Hadron Collider has just been upgraded, and is now making the highest energy collisions of any human-made machine ever. But even at 13 TeV, what are the prospects for testing String Theory, considering that the string energy scale should be up at around 10^19 GeV or so? Surprisingly, there are a number of phenomenological consequences that should emerge, and looking at what we've seen so far, they may disfavor String Theory after all.

Comments

Re:Which string theory?

[gstoddart]

Sure, but ... if Richard Feynmann

criticized string theory in an interview: "I don't like that they're not calculating anything," he said. "I don't like that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation--a fix-up to say, 'Well, it still might be true.': These words have since been much-quoted by opponents of the string-theoretic direction for particle physics.

I'll flat out admit I can't come close to understanding the voodoo which is string theory.

But that Feynman didn't either, and I've heard more recent quotes from physicists who basically say they don't know what it is either ... I feel I'm in good company.

I accept that my tiny little money brain isn't up to the task. But I'm not the only one saying "WTF?" about string theory.

Re:Which string theory?

[Anonymous Coward]

Feynman died in the mid 80s. We've had a good couple of "revolutions" in string theory since. Not that his comments aren't to be taken seriously, but the "string theory" he talked about then is not the "string theory" we talk about now. We now effectively have four or five "string theories" each of which are related to the others via "dualities" (ultimately, ways of transforming aspects of one theory to find exactly aspects of another), and are also related via a duality to supergravity. This both suggests that there is *something* interesting in the theories - be it pure mathematical or be it physical; now that we don't know - and also that there is a single theory that they are the limits of in various regimes. Enter M theory, a "theory" we know nothing about bar its limits in a few different regimes. (We don't know much about what those regimes are, either, merely that they exist.)

I'm no fan of string theory either, for many of the same reasons. I'm particularly no fan of the bullshit that comes along when "string phenomenologists" take some mathematical aspect, yank it out of context, apply it to some contrived setup in some higher-dimensional form of general relativity, and then pretend that any of this means anything. It doesn't, it means utterly fuck all. The people who instead pick some point of the string landscape and boil it down all the way to 3+1d spacetime are at least doing physics, even if to my knowledge few of them have found anything that suggests that they've got our universe out of it. The phenomenologists are just fucking around.

But at the same time, there's enough there that I'm happy people are working on it - I just wish that it wasn't such an enormous pit of funding and that other areas of high-energy theoretical physics would get more a look-in. I'm also not happy with the way that high-energy physics is presented to the public. On the one hand, we have people who've seen one Brian Greene documentary and think they know how the universe is set up, and on the other we have *Nobel laureates* giving plenary speakers at major conferences saying stupid, *stupid* fucking things like "We know that supersymmetry is real". No, you stupid fucking cunt, we do *not* know that. This was at a conference in Munich in, hmm, must have been 2008 or 2009. I was very offended even then, and the higher energy the LHC gets to and the increasing bouncing of MSSM parameters to lift them *just* out of range of the LHC, the more pissed off I get. Stupid. Fucking. Stupid. Fucking. Arrogant. CUNT.

I'm not sure I have a coherent point here :) I just like being able to call a Nobel laureate a stupid fucking cunt, and to advise slight caution against taking Feynman as the last word. A word worth listening to, definitely, but he wasn't talking about quite the same theory as we have now (and he was not, himself, infallible).

...and even more inaccurate than usual

[Roger W Moore]

There are several mistakes in the article as well. Supersymmetry is not a consequence of String Theory. It was invented to explain the huge difference between the Higgs mass and the energy scale where gravity becomes important (the fine-tuning or hierarchy problem). It was only after its invention that String Theorists realized that they needed it to make their theories work. In fact it is entirely possible that Supersymmetry exists and String Theory does not whereas the reverse is far less likely so it is wrong to say that SUSY is a consequence of String Theory.

Similarly the use of String Theory to solve non-perturbative QCD is not some new, fundamental principle but is simply a result of applying the maths developed for String Theory to a different problem. Hence studying the quark-gluon plasma is, at best, a test of some of the maths developed for String Theory but really tells us nothing at all about the physics. For a simpler analogy if you demonstrate that calculus works this does not imply that Newton's Laws of Motion are correct even though calculus was co-invented by Newton so he could write down and apply his laws.