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Four-thirds power law for knots and links

Abstract

Physical knot theory has recently been applied to polymer dynamics, and specifically to gel electrophoresis of DNA1,2. Knot energies3,4,5,6 measure the complexity of a knot conformation; minimum energy conformations are considered canonical or ‘ideal’ conformations. The rope length of a knot is one such measure of energy6, and an approximately linear relationship between rope length and the average crossing number for minimum rope-length conformations of simple knots has been reported7. Here I show that a linear relationship cannot hold in general: the rope length required to tie an N-crossing knot or link varies at least between ˜N3/4 and ˜N.

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Figure 1: Knot conformations.

References

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Buck, G. Four-thirds power law for knots and links. Nature 392, 238–239 (1998). https://doi.org/10.1038/32561

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