The good folks at Princeton have been beavering away at the esoteric, abstrusely mathematical yet infinitely tantalizing relationships between string theories and gauge theories. The latter are the rather well-respected mathematical descriptions of how the bits and pieces of atomic nuclei interact; the former is what you get when you look at the dawn of time, the centers of black holes and the other places where our understanding throws up its hands, and you jump in with both feet. Or, at least that’s what string theory was, back in 1997 or so.
Today, we’ve come to recognize that physics has a strange property: ideas you invent in one place pop their heads up where you never expected. Thus, supersymmetry — a mathematical concept invented in the 1970s to make string theory look a little more like the real world — branched off to become its own field of inquiry. In trying to figure out the implications of supersymmetry, Ed Witten and company invented supersymmetric quantum mechanics, which (among other things) gives you a wickedly delightful insight into all the problems professors use to torture their undergraduate physics students in Quantum Mechanics I.
The journey from string theory to SUSY QM leaves behind the essential “stringiness” of the original theory, but over the past several years, we’ve seen a whole slew of results which suggest that the math invented to quantize gravity, break the hearts of black holes and hold the Big Bang in our hands is also applicable to other, more accessible situations. Does this mean that string theory is the right path to quantizing gravity and all the rest? No, not necessarily. Does it mean that we can get our teeth into the equations and use experiments to see if at least some of our ideas work? Yes. Is knowing about this arena of activity a key part of understanding what physicists are doing today? Again, the answer is yes.
You can really hear the writer stretching for metaphors in the ScienceDaily story based on Princeton’s press release: “Between the two road sections lay a seemingly unbridgeable mathematical gulf”, etc. If you look at the paper which provoked this release, or even its abstract, you can appreciate why the press office’s language gets so tortured:
In two remarkable recent papers the planar perturbative expansion was proposed for the universal function of the coupling appearing in the dimensions of high-spin operators of the N=4 super Yang-Mills theory. We study numerically the integral equation derived by Beisert, Eden, and Staudacher, which resums the perturbative series. In a confirmation of the antiâ€“de Sitter-space/conformal-field-theory (AdS/CFT) correspondence, we find a smooth function whose two leading terms at strong coupling match the results obtained for the semiclassical folded string spinning in AdS5. We also make a numerical prediction for the third term in the strong coupling series.
Clear as a kegger in a mud pit.
The press release tries to draw a layman-friendly picture, as I mentioned. At a slightly higher level of mathiness are Barton Zwiebach’s String Theory for Pedestrians lecture videos. (Yes, that’s the same Zwiebach who taught the class and wrote the book.) The AdS/CFT correspondence stuff appears in the second and third lectures of the three-lecture series.
(Tip o’ the string theorist’s beret to Peter Steinberg.)