Figure 2.

(a) The HN phase consists of a nested array of coherently rotating helical bundles, close packed into a hexagonal lattice and is given by level sets of the phase field . The centres of the bundles are simple zeroes in the function Θ^hex(ζ), while branch point singularities at the corners of the fundamental hexagon diverge as ζ^−1/2. (b) The compression energy for this phase field can be broken into two components (top) and (bottom). The inset shows the domain of integration, .