Gravity seminar - Patrick Nolan Seminar

Since ground based interferometry led to the first prospects of directly detecting gravitational waves, a fully relativistic calculation of the two-body problem has gone from being a mathematical interest to an observational necessity. Accurate waveforms from colliding massive sources (such as black hole binaries) are essential for discerning space-time oscillations from background noise, at a level where the effect of the orbiting particle's gravitational field on its own motion cannot be ignored. Alongside major developments in post newtonian (PN) and numerical relativity (NR), perturbative approaches have led to a new way of interpreting this problem, in which the particle interacts with its own 'gravitational force' field. This is known as the self force approach, and it has shown much promise in filling the gaps between the limits of PN and NR.

In this talk, I will briefly introduce the basic principles of the self force, before discussing the issue of gauge freedom in our calculations. It turns out that the self force itself is not a gauge invariant quantity, reflecting the unphysical interpretation of the force as something separate from the background space-time. A major breakthrough for the field has been the construction of gauge-invariant quantities, which provide a direct connection with the underlying physics of the system. I introduce several recently discovered gauge-invariant quantities, and finally present numerical progress in looking at the properties of these quantities.