| Abstract: | 2d spin chains are a well established tool in describing condensed matter systems. A cute miracle in 2d is that in some cases the 2d spin chain happens to be integrable. Such cases include the spectrum on spinons in KCuF3 and the Hubbard model. Recent development in quantum field theory in four dimensions uses exactly the same techniques. For example, the most advanced (three loops) computation of scattering amplitude in a 4d gauge theory rely on a 2d spin chain description. No Feynman diagrams are involved! In another example, the conformal dimensions of local operators in the 4d theory are solved by mapping them to energies of an integrable spin chain. |
