2026/07/17 by Ting Xiao, Fan Wang, Li-Feng Yin
#math.AP
In this paper, we study the Schrödinger--Bopp--Podolsky system \begincases -Δu + V(x)u + ϕu = f(x,u), in ℝ3, -Δϕ+ a2 Δ2 ϕ= 4πu2, in ℝ3. \endcases We consider the case where the potential \(V\) is indefinite so that the Schrödinger operator \(-Δ+ V\) has a finite-dimensional negative space. Under suitable assumptions on the potential \(V\) and nonlinearity f(x,u), we prove the existence of nontrivial solutions via a local linking argument and Morse theory. Moreover, these solutions are shown to decay exponentially at infinity. Additionally, a ground state solution is obtained by minimization techniques. Finally, if \(f(x,u)\) is odd with respect to \(u\), we obtain an unbounded sequence of solutions using the symmetric mountain pass theorem.