The elementary constituents of matter studied in current high-energy physics experiments appear as point-like objects. The interactions among these particles are so far successfully described by a theoretical framework known as quantum field theory, gauge theories being an important example for the formulation of the particle physics Standard Model (SM). At large scales, the behaviour of our Universe is well explained by Einstein's General Relativity, a classical field theory describing gravity in geometrical terms. However, as the Large Hadron Collider (LHC) is entering its discovery phase and the Planck Space Observatory is harvesting high precision data, our current theories will soon face some new stringent tests. It is widely expected that both the SM and General Relativity turn out to describe reality only in an approximate fashion.
String Theory may be seen as a generalisation of the field theory framework on which the SM is based: in string theory the fundamental constituents are one- or multi-dimensional objects (i.e. strings and branes) that can vibrate. String theory implies some surprising new features with respect to the SM, such as the existence of extra space-time dimensions and a new type of symmetry between matter and forces, called supersymmetry. Moreover, while at large distances the theory agrees with General Relativity, it predicts interesting novelties also in the description of the gravitational force.
Research at Queen Mary aims to expand our knowledge of string and quantum field theories both at the conceptual and the computational level. A surprising feature of string theory is its ability to generate new ideas and techniques that can be employed in different contexts. A recent example of this, which is relevant for the current proposal, is the string-inspired relation between a certain type of interaction among gluons (MHV amplitude) and the geometrical problem of finding the area whose boundary is a particular polygon (Wilson loop). Research at Queen Mary contributed to the understanding of this relation and is actively studying new and powerful ways to calculate amplitudes without using the traditional approach of Feynman diagrams. Particular attention is devoted to a very special case of the gauge theory, known as N=4 super Yang-Mills. These new techniques are being generalised to handle other interesting quantities beyond the physical amplitudes and are being applied to different quantum field theories.