Blue phase defect theory

From the experimental results discussed in the above section, it is known that BPI and BPII have cubic structures. There are two theories that have successfully explained the existence of the blue phases and predict their symmetry and physical properties. One is known as the defect theory, in which the blue phases consist of packed double-twist cylinders and there... 

A defect theory for blue phases was introduced by Meiboom, Sethna, Anderson, et al. [22-27]. In this theory, the liquid crystal is assumed to form double-twist cylinders where the liquid crystal molecules twist about any radius of the cylinder, as shown in Figure 13.6. The cylinder cannot, however, cover the whole 3-D space without topological defects. Instead of a single cylinder, the blue phases consist of packed double-twist cylinders. There are defects in the regions not occupied by the cylinders. 

One can think of the blue phase as a lattice of double-twist tubes (which necessitates a lattice of disclinations) or a lattice of disclinations (which necessitates a lattice of double-twist tubes) [20]. Thus, a theory involving a lattice of double-twist tubes becomes implicitly a theory for a lattice of defects. 

The defect theory of blue phases was initially introduced by Meiboom, Sethna, Anderson, and Brinkman [5], [6], [12], [41], [42], [43], For detailed reviews see Sethna [9] and Wright and Mermin [20]. 

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