The 3D strict separation property for the nonlocal Cahn-Hilliard equation with singular potential

Abstract: We consider the nonlocal Cahn-Hilliard equation with singular (logarithmic) potential and constant mobility in three-dimensional bounded domains and we establish the validity of the instantaneous strict separation property. This means that any weak solution, which is not a pure phase initially, stays uniformly away from the pure phases $\pm1$ from any positive time on. This work extends the result in dimension two for the same equation and gives a positive answer to the long standing open problem of the validity of the strict separation property in dimensions higher than two. In conclusion, we show how this property plays an essential role to achieve higher-order regularity for the solutions and to prove that any weak solution converges to a single equilibrium.