Elastic strings in solids: Thermal nucleation

Thermal nucleation of kink-antikink pairs in an elastic string subjected to a washboard potential is analyzed in the limit of low temperature and high damping. The pair nucleation rate is calculated analytically for any value of the tilt up to close the instability threshold. Finite-size effects are quantified by computing the relevant end-point nucleation rate under a wide class of boundary conditions. Applications to the physics of lattice dislocations and flux lines in type-II superconducting materials are outlined.