Note on the multiplicity of solutions for nonlinear scalar field equations with a critical inverse-square potential
Bartosz Bieganowski, Daniel Strzelecki
TL;DR
This work addresses the multiplicity of solutions to a nonlinear scalar field equation with the critical inverse-square Hardy potential at the threshold of coercivity. By formulating the problem in the enlarged energy space $X^1(\mathbb{R}^N)$ and leveraging the oddness of the nonlinearity $g$, the authors apply Ikoma's abstract critical point theorem within symmetry-restricted subspaces to generate infinitely many radial and nonradial standing-wave solutions. The main contributions include proving the existence of an unbounded sequence of solutions with $P(u_j)=0$ and establishing regularity, extending multiplicity results to a singular, non-coercive, non-translation-invariant setting. The results have implications for standing waves of nonlinear Schrödinger equations with critical inverse-square potentials and illustrate how symmetry and variational methods overcome the lack of coercivity.
Abstract
We are interested in the multiplicity of solutions to the following scalar field equation $$ -Δu - \frac{(N-2)^2}{4|x|^2} u = g(u), \quad \mbox{in } \mathbb{R}^N \setminus \{0\}. $$ We establish the existence of infinitely many radial and non-radial solutions.
