The Case Against Smooth Null Infinity or the Behaviour of Gravitational Radiation in the Asymptotic Regime

In this talk, I will present research in the direction of understanding the asymptotic behaviour of gravitational radiation in spacetimes that are dynamically constructed from physically motivated assumptions.

More precisely, I will describe how to set up and solve the scattering problem around spacelike infinity for the linearised Einstein vacuum equations around Schwarzschild with characteristic scattering data posed towards and along past null infinity.

I will then describe how to pick scattering data that model the exterior of $N$ infalling bodies from the infinite past, and I will show how to compute the global asymptotic behaviour of the resulting solutions. In particular, this will show that the latter fail to admit a smooth future null infinity or the usual expansions of Bondi coordinates, while at the same time providing an alternative framework for the asymptotics of gravitational radiation, which, in particular, gives constructive corrections to both Bondi coordinates and the notion of a smooth null infinity.