Coarsening dynamics in uniaxial nematic liquid crystals

We study the coarsening dynamics of defects in the uniaxial nematic liquid crystal 4-cyano-4’-n-pentylbiphenyl, subjected to a rapid pressure jump from the isotropic to the nematic phase. The defect tangle formed at the phase transition is dominated by type-1/2 strings (disclination lines), but also contains type-1 strings and monopoles. We also give a general discussion of the existence of scaling solutions to the nematodynamic equations for loop collapse and two-dimensional vortex-antivortex annihilation. We have measured the density of type-1/2 strings and loops and the monopole density as a function of time. We have also measured the rate at which the intercommutation of two strings takes place. Surprisingly, although the type-1/2 string density ρ scales as expected as a function of time, ρ∼${\mathit{t}}^{\mathrm{-}1}$, loop densities and monopole densities do not seem to scale over the time interval studied. A possible explanation is given.