  Holographic duality provides a first-principles approach to investigate real
time processes in quantum many-body systems, in particular at finite
temperature and far-from-equilibrium. We use this approach to study the
dynamical evolution of vortex number in a two-dimensional (2D) turbulent
superfluid through numerically solving its gravity dual. We find that the
temporal evolution of the vortex number can be well fit statistically by
two-body decay due to the vortex pair annihilation featured relaxation process,
thus confirm the previous suspicion based on the experimental data for
turbulent superfluid in highly oblate Bose-Einstein condensates. Furthermore,
the decay rate near the critical temperature is in good agreement with the
recently developed effective theory of 2D superfluid turbulence.
