Precision calculations in field theories and in string theory and the relations between them

My field of research is string theory, a very advanced theoretical construct that allows for the unification of all the forces of nature. String theory has different limits, in some the dominant effects are gravitational and in others they are field-theoretical. The application of string theory as a unified theory of nature is not mature yet, but is a very exciting possibility. Until the day comes when we can use strings to make experimental predictions we try to gain a better understanding of the theory and try to learn from it about other questions in theoretical physics. That is the direction I pursue in my research. As stated above, we can isolate from string theory some subsectors, which are described by simpler theories. In particular, what are known as gauge theories (the simplest of which is elecro-magnetism). The realm of subatomic particles is well described by one such theory (know as ``the standard model of particle physics''). This theory can be realized in string theory by rather complicated constructions. There is another gauge theory with a beautifully simple realization in string theory, commonly known as N=4 supersymmetric Yang-Mills. The simple manifestation of this theory in string theory allows us to make precise calculations both at strong and weak coupling and compare the results, often with surprising agreement. While this theory is probably not realized in nature, it is similar in many ways to the standard model of particle physics. A better understanding of this theory should lead to better calculational tools for particle physics. While this theory is simpler (in some ways) than the standard model, it is still quite rich and complicated. My specific research focuses on identifying subsectors of the theory where exact results can be obtained. Several such subsectors are known (and I have contributed to their understanding) and the purpose of my research is to find more such subsectors, understand the known ones better and enlarge them to include more calculable quantities. The ultimate goal of this line of research is to have a complete understanding of this theory, where all quantities can be calculated. This goal seems quite far from being attained at the moment, but remarkable progress has been achieved over the past few years that gives hope that this goal is not completely out of reach. Whether we reach that target or not, a better understanding of this theory promises to have other applications in theoretical physics. It could have applications in other corners of string theory, or even for condensed matter physics, which uses some of the same tools used in studying N=4 Yang-Mills. Furthermore, it could help understand the standard model and in particular QCD, the theory of the strong interactions. That theory is strongly coupled and understanding how other theories behave at strong coupling could shed light on this theory too.