Hedgehogs radial

Fig. 3.5.10. Singular points in droplets (a) spherically symmetric radial (hedgehog) configuration with the director normal to the surface (b) bipolar structure with the director tangential to the surface (c) singular points in a capillary.

Fig. 8.29 Structure of some defects in the SmA phase, namely, cylinder (a), semi-sphere (b), and radial hedgehog (c) and a monopole in SmC (d)...

Many structural defects compatible with the incompressible smectic layers can be observed under a microscope. Among them are cylinders, tores and hemispheres observed at the surfaces, radial hedgehogs observed in smectic drops, etc. Three of them are presented in Fig. 8.29a-c. Note that in aU defect structures of this type, the splay distortion plays the fundamental role but bend and twist are absent. Other, more special defects, namely, the walls composed of screw dislocations, are observed in the TGBA phase. 

We now turn to radial droplets for which, in absence of external fields (with 1) = 0) and for T = 0.8 the hedgehog -like structure is stable. As discussed above, the spectrum of the radial droplet for 7/ = 0 is the Pake-type powder pattern consisting of two asymmetric peaks at S(jJqS [25],... 

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