Multiplicity results for fractional Laplace problems with critical growth

This paper deals with multiplicity and bifurcation results for nonlinear problems driven by the fractional Laplace operator $(-\Delta)^s$ and involving a critical Sobolev term. In particular, we consider $$\begin{cases} (-\Delta)^su=\gamma|u|^{2^*-2}u+f(x,u) & \mbox{in } \Omega u=0 & \mbox{in } \mathbb R^n\setminus \Omega, \end{cases}$$ where $\Omega\subset\mathbb R^n$ is an open bounded set with continuous boundary, $n>2s$ with $s\in(0,1)$, $\gamma$ is a positive real parameter, $2^*=2n/(n-2s)$ is the fractional critical Sobolev exponent and $f$ is a Carath\'{e}odory function satisfying different subcritical conditions.