"Hidden symmetries and decay for the wave equation on the Kerr spacetime" by Lars Andersson and Pieter Blue is to appear in the Annals of Mathematics and can be found at http://annals.math.princeton.edu/articles/9459.The Kerr spacetime describes stationary, rotating black holes. Since the 1970s, it had been known that the Kerr spacetime has a hidden symmetry, a particular type of generalisation of classical symmetries, like rotation. The existence of the hidden symmetry explained why, in the Kerr spacetime, many of the key equations of mathematical physics – such as the wave and Hamilton-Jacobi equations – are separable. The new paper introduces a method that uses the hidden symmetry to prove boundedness and decay of solutions to the wave equation, without using separation of variables.

The Annals of Mathematics is widely recognised as one of top two journals in Pure Mathematics; it is famously selective, publishing only about 50 papers per year after a rigourous (and often lengthy) refereering process.