Recently there has been a huge activity and progress in calculating tree and one-loop amplitudes for gauge and gravity theories using twistor space inspired methods as well as techniques based on unitarity cuts. The activity was initiated by a paper by Witten, which suggested that perturbative N=4 SYM has a dual description as a topological string theory in twistor space. In this talk we will focus on the progress in calculating one-loop amplitudes and discuss how twistor space inspired and unitarity techniques can be applied with great success to calculate loop amplitudes.

University of Wales Swansea