It’s knot what you know
Why is it that some knots seem to hold tight while others readily slip apart? Patil et al. develop a theoretical analysis of the stability of knots and find links between topological parameters (twist charge, crossing numbers, handedness) and mechanical stability. The theory is confirmed using simulations and experiments on color-changing fibers that optically show localized stress differences in different parts of the knot as the two strands are pulled apart. The authors show why some common knots slip easily and untie, whereas others hold tight.
Science, this issue p. 71
Knots play a fundamental role in the dynamics of biological and physical systems, from DNA to turbulent plasmas, as well as in climbing, weaving, sailing, and surgery. Despite having been studied for centuries, the subtle interplay between topology and mechanics in elastic knots remains poorly understood. Here, we combined optomechanical experiments with theory and simulations to analyze knotted fibers that change their color under mechanical deformations. Exploiting an analogy with long-range ferromagnetic spin systems, we identified simple topological counting rules to predict the relative mechanical stability of knots and tangles, in agreement with simulations and experiments for commonly used climbing and sailing bends. Our results highlight the importance of twist and writhe in unknotting processes, providing guidance for the control of systems with complex entanglements.
- Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2) – Science Magazine
- England coronavirus testing has not risen fast enough – science chief – The Guardian
- Coronavirus Tests Science’s Need for Speed Limits – The New York Times
- Trump Falsely Distorts New York Times COVID-19 Science Story – FactCheck.org
- This is the brightest supernova ever seen – Science Magazine
- Coronavirus Today: Science will save us – Los Angeles Times
- Italians stuck at home are measuring light pollution for ‘science on the balcony’ – TechCrunch
- ‘Oumuamua might be a shard of a broken planet – Science News
- College of Arts and Science converts thriving academic programs to departments – Vanderbilt University News