Existence and Uniqueness for the Fractional Gelfand Equation in $\mathbb{R}$

Abstract

We prove existence, symmetry and uniqueness of solutions to the fractional Gelfand equation $$ (-\Delta)^s u = e^u \quad \mbox{in $\mathbb{R}$} \quad \mbox{with} \quad \int_{\mathbb{R}} e^u dx < +\infty $$ for all exponents $s \in (\frac{1}{2},1)$. Furthermore, we show $u$ has finite Morse index and that its linearized operator is nondegenerate. Our arguments are based on a fixed point scheme in terms of the function $v= \sqrt{e^u}$ and we devise a nonlocal shooting method involving (locally) compact nonlinear maps. We also study existence, symmetry and uniqueness of solutions to $(-\Delta)^s u = K e^u$ in $\mathbb{R}$ with $K e^u \in L^1(\mathbb{R})$ for a general class of positive, even and monotone-decreasing functions $K > 0$.