COVID-19 ad ban in Germany led to 6% reduction in grocery sales

In spring 2021, during the height of the COVID-19 pandemic, one of Germany's 16 federal states instituted an ad ban, forcing retailers to stop all print advertising in that state for three weeks. The state did so under the ...

Observation of 3D acoustic quantum Hall states

The quantum Hall effect (QHE) is one of the most notable discoveries in condensed matter physics, opening the door to topological physics. Extending QHE into three dimensions is an inspiring but challenging endeavor. This ...