Jieci Wang

Light usually behaves like a pedestrian on a two-way street: the path from a streetlamp to a camera matches the reverse path. But near a rotating black hole with broken spatial symmetry, this street becomes one-way. Swap the light source and observer, and the hole's shadow changes shape: from an oval resembling a rugby ball, it turns into a teardrop.

Ordinary water freezes as expected. But sometimes hot water turns to ice faster than cold — the Mpemba effect. Recently, a similar rule-breaking was found in quantum entanglement — the invisible link between particles discovered by Erwin Schrödinger.

Every pulsating object has a moment when its rhythm falters. For boson stars, hypothetical clumps of ultralight particles, that moment turns out to be the point where mass stops growing. The authors calculated the lowest radial mode (the fundamental 'breathing' tone) for a whole family of such stars, including models with self-interaction.