Ian Jones (Southampton)

I am now in my final year of a post-doc sponsored by the British government. Nevertheless, my field of research is very closely related to that of the Network, and so I've written a brief description of the main area of overlap. I'd like to add that although I will start a post-doc in Penn State this coming September, I hope to continue collaborating with people within the network while I'm abroad.

My main research project is a numerical one: I have written a code to time evolve the linearised perturbation equations of a rotating Newtonian star. The unperturbed background is simply the stationary axisymmetric one appropriate to the star's rotation rate and central density, and is calculated in a separate numerical code. An arbitrary perturbation is then superimposed on this background and evolved using 2-step Lax-Wendroff finite differencing. To ensure that the code runs reasonably rapidly on a standard PC, all perturbations are decomposed into the basis , and the perturbation in each separate m is evolved separately. The code is therefore two-dimensional in space.

The motivation behind this work is to provide a test-bed for new ideas and formulations before they are incorporated into full-scale three-dimensional hydro codes. In particular, we in Southampton are interested in implementing a local gravitational radiation reaction force, to observe the growth of a CFS-unstable mode, including both mass and current multipole contributions.

This has naturally created two collaborations within the network. Firstly, I have visited the Meudon group several times to learn about the LORENE package, which I am now using to solve the Poisson-type equations which inevitably arise in calculating the radiation reaction force. I hope that from this point on I will be able to develop my code without too much assistance, emailing the Parisians when I get stuck. LORENE is written in C++, a language which I have not encountered before, so much of my time has been spent trying to understand unfamiliar coding techniques.

Secondly, the derivation of the radiation reaction formulae is a problem in post-Newtonian theory. The Jena group are the experts in this, and so once I have mastered the issues involved in numerically solving Poisson-like equations, I will work with Guillaume Faye in implementing the full radiation reaction equations. I hope to begin this phase of the project very soon.