Less is more

A tight grip can be counterproductive

3:48pm, May 7, 2008

What’s true for jealous lovers and frustrated parents also applies to nanoscale cogs and wheels and environmental regulations: Cutting some slack sometimes gives better results than being too strict.

Giovanni Volpe, a physicist at the Institute for Photonic Sciences in Barcelona, and his colleagues took a fresh look at the mathematics of constraints — specifically, of “noisy” constraints. That’s when both the constrained object and the stuff that’s constraining it experience small, random fluctuations, or noise.

An example, Volpe explains, is the atomic force microscope, a tool that can sense and impart tiny forces on objects as small as single atoms, but has limited accuracy because of thermal vibrations. Other examples include molecular machines that transport stuff within living cells while attached to microscopic strings — again a situation where thermal shaking is relentless.

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