Prof. Iain W Stewart

Professor Stewart's research interests involve theoretical nuclear and particle physics. In particular, he focuses upon the development and application of effective field theories to further our understanding of Quantum Chromodynamics (QCD).

The idea of an effective field theory is to combine the relevant degrees of freedom and symmetries of a system, together with a power counting expansion, into a predictive framework. Different effective theories can be used to describe various limits of QCD in a model independent way. This approach complements lattice QCD since direct numerical simulations are often computationally difficult, whereas lattice simulations of effective theory quantities can be tractable.

Professor Stewart's past research has been in the areas of Heavy Quark Effective Theory (for b quark decays), Non-Relativistic QCD (for quark-antiquark systems), Chiral Perturbation theory (for low energy pions and kaons), and Nucleon Effective Theory (for two nucleon or deuteron systems). Recently, he has been developing an effective theory framework to describe the interaction of energetic quarks with collinear and soft gluons (now referred to as the Soft-Collinear Effective Theory). The formalism can be applied to many processes that are of interest for the study of CP violation from B-meson factories, as well as to improve the understanding of more traditional hadronic reactions. This framework provides a method for dealing with power corrections, which were previously considered to be intractable or model dependent.