Hydrodynamic and Rayleigh-Plateau Instabilities of Q Strings

As analogues of compact objects, solitons have attracted significant attention. We reveal that cylindrical Q strings exhibit a dynamical instability to perturbations with wavelengths exceeding a threshold λ>λ_{c}. This instability can destroy the invariance in the cylindrical direction, as a generation mechanism for Q balls, similar to the formation of droplets. As the interface of Q strings approaches a thin wall, this long-wavelength instability degenerates into the Rayleigh-Plateau instability with a threshold related only to the geometric radius λ_{c}=2πR. Such results indicate that Q strings, like black strings, resemble low-viscosity fluids with surface tension.