Global existence and stability of nearly aligned flocks

We study regularity of a hydrodynamic singular model of collective behavior introduced in \cite{ST1}. In this note we address the question of global well-posedness in multi-dimensional settings. It is shown that any initial data $(u,\rho )$ with small velocity variations $\mathrm{\mid }u(x)-u(y)\mathrm{\mid }<\text{e}$ relative to its higher order norms, gives rise to a unique global regular solution which aligns and flocks exponentially fast. Moreover, we prove that the limiting flocks are stable.