Amplitudes, Strings and Branes

The theory of scattering amplitudes has seen rapid progress over recent years, with development on many fronts, often driven by the huge success in applying on-shell methods. New symmetries and integrable structures in the the scattering amplitudes of planar N=4 super Yang-Mills theory have led to new formulations of the problem of calculating scattering amplitudes. The duality to light-like Wilson loops has led to the application of OPE techniques to constrain loop corrections to scattering amplitudes, with a striking similarity to the application of Regge theory on the amplitude side. At strong coupling, techniques from integrable systems have been applied to the corresponding minimal surface problem. In perturbation theory, recursive techniques allow the construction of the integrand to all loop orders while the algebraic and analytic structure of multi-variable polylogarithmic functions has been a crucial tool in studying the integrated amplitudes. In many settings the natural language for the above developments is twistor theory. Trying to unify the above ideas to understand scattering amplitudes at finite coupling will be one of the main challenges in the near future. There has been much related progress in understanding amplitudes beyond 4d gauge theories. Progress in the theory of M2-branes has led to new 3-dimensional superconformal field theories which can be studied using similar techniques to those in four dimensions, revealing similar integrable structures. Applications of on-shell methods have led to new ideas regarding the ultra-violet properties of gravitational theories with much focus on the maximal N=8 supergravity theory. Recently, new and surprisingly simple formulations of tree-level gravitational amplitudes have been found indicating that there is still much to be understood about the structure of amplitudes in such theories. In turn there have been recent advances in understanding the structure of string theory scattering amplitudes. KLT-type relations between open and closed string amplitudes have suggested a powerful duality between color and kinematics in gauge and gravity amplitudes. Pure spinor methods have been used to derive general N-point disk amplitudes. Meanwhile, progress has been made in defining superstring perturbation theory at multi-loop level. Ideas from twistor string theory have also led to interesting new techniques in field theory. The institute aims to encourage experts in the field to exchange and develop ideas further in an environment allowing for plenty of discussion. Organizers: J. Drummond, H. Johansson, N. Lambert, M. Spradlin, A. Volovich