Abstract:

Our purpose of this paper is to study weak solutions of nonlinear Helmholtz equation (0.1) $-\Delta u-u=Q|u{|^{p-2}}u+\sum\limits_{i=1}^N{{k_i}}{\delta_{{A_i}}}$ where $p>1$, $k_i\in$$\mathbb{R}$\{0} with i=1, …, N, Q: $\mathbb{R}^2$→[0, +∞) is a Hölder continuous function and ${\delta_{{A_i}}}$ is the Dirac mass concentrated at ${{A_i}}$.We obtain two solutions of (0.1) if $k=\sum\limits_{i=1}^N{|{k_i}}| < {k^*}$ for some $k^*$>0 when $Q$ decays as $|x|^{α}$ at infinity with $α ≤$ 0 and $p$>max{2, 3(2+$α$)}. These two sequences of solutions of (0.1) are sign-changing real-valued solutions with isotropic singularity at ${{A_i}}$ by applying Mountain Pass Theorem to an related integral equation. By using the iteration technique, we obtain the decays of solution of (0.1) controlled by $|x|^{-\frac12}$ at infinity when $p>\max\{2, 4(2+\alpha)\}$.

Key words: Helmholtz equation, Isolated singularity, Mountain pass theorem