Our work focusses on using Numerical Relativity, the simulation of Einstein's Equations of GR on a supercomputer, to solve outstanding questions about dark matter and early universe cosmology.
Axion StarsAxion or axion-like particles are a potential dark matter candidate. In the classical limit, axions may be described as a light scalar field with a cosine-like self-interaction potential, minimally coupled to gravity. Long lived "axion star" solutions to the evolution equations have been found numerically. These are localized perturbations of the field and the spacetime geometry which oscillates in time. We study interactions of these solutions, their collapse and dispersal, which may have implications for observations of dark matter halos.
We study massive vector fields, which may result from physics beyond the standard model, or the effective photon mass in a plasma. Search fields develop a superradiant instability in the presence of black holes, on timescales.
Inhomogeneous CosmologyInflation is invoked as a solution to the horizon problem in cosmology. However, many conventional slow-roll models do not support a long term inflationary period unless space is near to begin with, which makes the inflationary paradigm rather self-defeating. This is particularly true of "small field" models, favored as low energy effective theories of high energy gravity models (eg, string theory). We study the robustness of the inhomogeneities in the inflation field and the spacetime metric, in order to develop an understanding of the factor.
GRChomboOur work is part of the GRChombo collaboration. GRChombo is a new numerical relativity code. GRChombo's features include fully adaptive mesh refinement (AMR) with block-structured Berger rigsos grid generation which supports non-trivial "many-boxes-in-many-boxes" meshing hierarchies, and massive parallelism through the Message Passing Interface (MPI). For more information, videos of our simulations and details of our publications, visit the GRChombo website .
Working with usProjects for Bachelors or Masters students may also be available in these areas for motivated students. Whilst a knowledge of GR and / or numerical simulation would be helpful, this is an area beyond the standard undergraduate course material and practical skills developed therein. The main requirement for students is a willingness to learn.
We especially encourage applications from traditionally underrepresented groups in physics, such as female and minority candidates.