Gravity Seminar: Rita Santos, Support Scientist UIB – Characteristic Critical Collapse with Null Infinity

Solutions to the Einstein Equations that are close to the threshold of black hole formation exhibit features that resemble critical phenomena in statistical mechanics. We thoroughly study the critical collapse of a scalar field and a Yang-Mills field, focusing both on local and global aspects of such collapses. First, we show that the collapsing fields have local Discretely Self-Similar (DSS) behaviour. Remarkably, global quantities such as the Bondi mass and News Function manifest the same DSS behaviour. Second, the mass of black holes formed in evolutions near the threshold is shown to scale as a function of the distance to the critical parameter. Lastly, we show that these results are universal with respect to the initial data. Our numerical scheme is based on a characteristic formulation in compactified Bondi coordinates, with methods that are globally fourthorder accurate. The convergence of the code is tested, and the accuracy is improved by employing analytical mesh refinement.