Disclinations nonsingular

When L/p I, the cholesteric does not differ much from the nematic phase. No wonder therefore that optical observations for weakly twisted cholesterics reveal thick (nonsingular) and thin (singular) line defects —disclinations similar to that in the nematic phase. Moreover, in droplets of the so-called compensated cholesteric mixtures with extremely small Ljp one can observe point defects [6] which, from the topological point of view, are allowed only in a nematic phase. 

Classes Cx, C, and Cjf correspond to n rotations of directors when one goes once around the disclination s core for example, Cx relates to rotations of X and t (A remains nonsingular). Class Co corresponds to 2n rotations unlike their nematic counterparts, these lines are topologically stable. Class Co describes topologically unstable 4 r disclinations. 

As already discussed, there are no isolated point defects in the cholesteric phase, 7r2(9 = SO 3)/D2) = 0. However, singular point defects can serve as the ends of linear solitons, as in the case of the monopole structure, in which the nonsingular disclinations can be considered as linear solitons. 

J. Bezic and S. Zumer, Chiral nematic liquid crystals in cylindrical cavities A classification of planar structures and models of nonsingular disclination lines, Liq. Cryst. 14, 1695 (1993). 

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