How does the "tube diameter" of an entangled polymer melt,
which determines the magnitude of elastic effects in flow, arise from interplay of stiffness and bulkiness of the chains, with topological uncrossability?
Entanglements between chains can be identified in a simulated polymer melt, by fixing the chain ends and "shrinking" the chains without letting them cross,
so they "draw up" into straight paths between crossings. Is there a more "noninvasive" way we can find the tube in simulations?
Chain-shrinking algorithm applied to simulated melt results in chain paths consisting of a sequence of straight segments between entanglement points. From Everaers et al. Rheology and microscopic topology of entangled polymeric liquids. Science (2004) 303, 823.)