M-theory, Cosmology and Quantum Field Theory

The research programme of the Theoretical Physics Group at Imperial College London is focused on the interrelated fundamental problems of quantum gravity, quantum field theory and cosmology. Our approaches to the problems of quantum gravity derive principally from superstring theory and supergravity and from the hypothesised parent theory of both these approaches known as M-theory. One important target of our work will be the relations between string theory and non-perturbative Yang-Mills gauge theory which can be derived using duality relations and exactly integrable quantum field theory models. In particular, we hope to obtain exact information about the quantum string theory spectrum and the relations between string theory and important Yang-Mills gauge theory phenomena such as confinement. The relations between string theory and Yang-Mills gauge theories have developed to the point where concrete physical predictions can be made about strong interaction physics in systems such as quark-gluon plasmas, which may be explored at the LHC collider at CERN. A second major target of our research will be to analyse the many vacuum states of string theory by extending our work on explicit solutions to the associated supergravity field equations. Infinite classes of such solutions with unbroken supersymmetry have been found, and we intend to extend this understanding to the spectral properties of the theory near these vacua. Another feature of string and supergravity theories which we shall investigate is the large class of duality symmetries they display, and how these lead to new kinds of global solutions where spacetime geometry and quantum fields are interrelated, known collectively as generalised geometry. We also have extensive expertise in the application of numerical techniques to the study of string and supergravity solutions, and we will further develop these and also apply them to the properties of black holes. In the area of cosmology and related aspects of quantum field theory, key clues to the structure of the big bang origin of the universe are to be found in the non-Gaussian corrections to the cosmic microwave background. This is an important indication about the origin of density perturbations in the early universe and of the formation of galactic structures. We have established participation both in observational programmes such as Planck, Spider and BPol, and also in the analysis of this data. On the other hand, fully developed models are needed of the evolution of quantum fields in the early universe and their effect on the evolution of early universe structure. So, in parallel with the analysis of observational microwave background data, we will pursue computational modelling of early-universe field dynamics and structure formation. There is a deep synergy between the broad strands of our research, with work on the non-perturbative aspects of Yang-Mills gauge theories informing both supergravity and superstring theory on the one hand and the study of high-temperature fields in the early universe and the computational modelling of early-universe density fluctuations on the other. Much of our work revolves around the problems of gravity and Yang-Mills gauge theories, both at a fundamental level and also in cosmology.