Cabada Fernández, AlbertoLópez Somoza, LucíaAshyralyev, AllaberenRuzhansky, MichaelSadybekov, Makhmud A.2026-01-072026-01-072024-08-28Cabada, A., López-Somoza, L. (2024). Characterization of the Constant Sign of a Class of Periodic and Neumann Green’s Functions via Spectral Theory. In: Ashyralyev, A., Ruzhansky, M., Sadybekov, M.A. (eds) Analysis and Applied Mathematics. AAM 2022. Trends in Mathematics(), vol 6. Birkhäuser, Cham. https://doi.org/10.1007/978-3-031-62668-5_5978-3-031-62668-5https://hdl.handle.net/10347/44915In this paper we characterize the regions of constant sign of the Green's fucntions related to operator $T_n[p,M]\,u(t)=u^{(n)}(t)+p\,u^{(n-2)}(t)+M\,u(t)$, with $n$ an even number, $n\ge 4$, and $p\le 0$, coupled to periodic or Neumann boundary conditions. The results generalize the situation considered in \cite{CabSom_Eloe} for the particular case of $p=0$.engSpectral characterizationNeumann ProblemPeriodic ProblemGreen's function1202 Análisis y análisis funcionalbook part10.1007/978-3-031-62668-5_5open access