# Nondecaying particle interactions

We have discovered a particle-particle interactions that have distance-independent strength. These are rare in physics, thus I am excited about this result. Learn more about the experiment from the paper or watch the video below

Published in Physical Review Letters, 2015.

An excerpt form a comment in Nature Physics:

These somewhat surprising results, the authors show, follow from simple theory. Imagine that one particle moves, stirring up a fluid flow. Some of the fluid will flow back past the particle, moving around its sides. Poiseuille’s law implies that the increase in pressure on the particle should be proportional to the channel length, and inversely proportional to the fourth power of its width. Another relation among these quantities comes from mass conservation around the moving sphere, and a third from elementary lubrication theory, which predicts the flow of a viscous liquid at a given pressure given a minimum gap width. Putting these relations together, the authors derive a formula for the mean flow in the channel, as it depends on channel width R and length L. Significantly, the simple 1/L dependence of the flow — and hence on the force between two particles, independent of the distance between them — drops out, in perfect agreement with the experiments.

Misiunas and colleagues speculate that biology probably already exploits this effect in enhancing biochemical control over the extended distances of whole cells. For example, myriad processes within cells require molecular diffusive transport through narrow channels. Such diffusion, they argue, occurs about 40% faster than it otherwise would as a result of the long-distance flows. It’s surprising that such a simple effect could have gone undetected for so long. We typically think of geometric confinement as a restriction, yet, paradoxically, it can also be a resource.

by Mark Buchanan.

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