How tangled is a tangle

Abstract New measures of algebraic, geometric and topological complexity are introduced and tested to quantify morphological aspects of a generic tangle of filaments. The tangle is produced by standard numerical simulation of superfluid helium turbulence, which we use as a benchmark for numerical investigation of complex systems. We find that the measures used, based on crossing number information, are good indicators of generic behaviour and detect accurately a tangle’s complexity. Direct measurements of kinetic helicity are found to be in agreement with the other complexity-based measures, proving that helicity is also a good indicator of structural complexity. We find that complexity-based measure growth rates are consistently similar to one another. The growth rate of kinetic helicity is found to be twice that of energy.

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