Null infinity as a weakly isolated horizon
Null infinity as a weakly isolated horizon
Null infinity, ${\mathcal{I}}^{+}$, arises as a boundary of the Penrose conformal completion $(\stackrel{^}{M},{\stackrel{^}{g}}_{ab})$ of an asymptotically flat physical space-time $(M,{g}_{ab})$. We first note that ${\mathcal{I}}^{+}$ is a weakly isolated horizon (WIH) in $(\stackrel{^}{M},{\stackrel{^}{g}}_{ab})$, and then show that its familiar geometric properties can be derived from the general WIH framework. This …