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Optimal Control

Optimizing the energy efficiency of driving processes provides valuable insights into their underlying physics and is of crucial importance for numerous applications, from biological processes to the design of machines and robots.

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Curveball at the microscopic scale

The Magnus effect causes the curved trajectory of spinning footballs or tennis balls, and it can even be used for the propulsion of ships. A team of physicists led by Clemens Bechinger have now documented, for the first time, the existence of the Magnus effect at the microscopic scale.

Whether you are familiar with the Magnus effect or not, you have certainly often made use of it, e.g. when kicking a curveball or putting spin on a tennis ball. The Flettner rotor even employs this principle to…

Why selfishness can lead to fairness

The reason why many animals organize themselves within herds is not necessarily the result of gregariousness or social behaviour. One example is seals: On their own, they are easy prey for orcas or sharks. Instead, it is much safer within a group, because then the danger of an attack is spread out among many individuals. It is safest in the middle of the group where animals are crowding together in a very small space and an attack there is more likely to target a close neighbor than oneself. At…

Surface melting of a colloidal glass

Despite their technological relevance, a full microscopic understanding of glasses is still lacking. This applies even more to their surfaces whose properties largely differ from that of the bulk material. Here, we experimentally investigate the surface of a two-dimensional glass as a function of the effective temperature.

The role of cohesion in the flow of active particles through bottlenecks

When particles are forced through a sufficiently narrow geometric constriction, their flow becomes unsteady due to the development of temporary clogs, e.g. arches, which strongly perturb their free motion. Such behavior has been studied in great detail, e.g. for granular matter driven through funnels or colloidal particles flowing through geometric constraints.

Moving furniture in the micro-world

Have you ever noticed when moving furniture that heavy objects are easier to move if you rotate them at the same time as you push? Many people intuitively do this right. An international research team from Konstanz (Germany), Trieste and Milan (Italy) has now investigated this phenomenon – the reduction in static friction caused by simultaneous rotation – on the microscopic scale.

Barrier crossing in a viscoelastic bath

The hopping of an overdamped particle across a potential barrier, as originally considered more than 100 years ago by Svante and Arrhenius to understand chemical reaction rates is one of the oldest and most important problems in statistical physics...