Rigidity of minimizers in nonlocal phase transitions II

In this paper we extend the results of \cite{S3} to the borderline case $s = \frac 12$. We obtain the classification of global bounded solutions with asymptotically flat level sets for semilinear nonlocal equations of the type $$\Delta^{\frac 12} u=W'(u) \quad \text{in} \quad R^n,$$ where $W$ is a double well potential.