COARSENING DYNAMICS IN UNIAXIAL NEMATIC LIQUID-CRYSTALS

We study the coarsening dynamics of defects in the uniaxial nematic li quid crystal 4-cyano-4'-n-pentylbiphenyl, subjected to a rapid pressur e jump from the isotropic to the nematic phase. The defect tangle form ed at the phase transition is dominated by type-1/2 strings (disclinat ion lines), but also contains type-1 strings and monopoles. We also gi ve a general discussion of the existence of scaling solutions to the n ematodynamic equations for loop collapse and two-dimensional vortex-an tivortex annihilation. We have measured the density of type-1/2 string s and loops and the monopole density as a function of time. We have al so measured the rate at which the intercommutation of two strings take s place. Surprisingly, although the type-1/2 string density rho scales as expected as a function of time, rho is similar to t-1, loop densit ies and monopole densities do not seem to scale over the time interval studied. A possible explanation is given.