A Ghost in the Atom: How Vacuum Hides a Pseudoscalar
In 1976, Gerard 't Hooft noticed that the vacuum of a gauge theory is not as simple as it seems: it possesses a topological structure that manifests itself in a nonzero topological susceptibility.
Smoldering Embers of Black Holes
In 2017, the LIGO and Virgo gravitational detectors caught ripples in spacetime from the merger of two black holes 540 megaparsecs away. The event was named GW170814. But what remained after this cosmic collision? Besides distorted space, tiny black holes, or 'crumbs', might have been born.
When a Black Hole Can Split Apart
A black hole is like a spinning drop of viscous liquid. Normally, such a drop tends to stay whole: splitting would reduce its surface area, which contradicts the law of non-decrease of entropy (a measure of disorder, like a broken cup doesn't glue itself back together).