Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
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Hydrodynamics at the smallest scales: a solvability criterion for Navier–Stokes equations in high dimensions

Strong global solvability is difficult to prove for high-dimensional hydrodynamic systems because of the complex interplay between nonlinearity and scale invariance. We define the Ladyzhenskaya–Lions exponent αl(n)=(2+n)/4 for Navier–Stokes equations with dissipation −(−Δ)α in Inline Formula, for all n≥2. We review the proof of strong global solvability when ααl(n), given smooth initial data. If the corresponding Euler equations for n>2 were to allow uncontrolled growth of the enstrophy Inline Formula, then no globally controlled coercive quantity is currently known to exist that can regularize solutions of the Navier–Stokes equations for α<αl(n). The energy is critical under scale transformations only for α=αl(n).

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