On the spectral instability for weak intermediate triharmonic problems

We define the weak intermediate boundary conditions for triharmonic operator −Δ3. analyse sensitivity of this type upon domain perturbations. construct a perturbation (Ωϵ)ϵ > 0 smooth Ω ℝ N which on ∂Ωϵ are not preserved in limit ∂Ω, analogously to Babuška paradox hinged plate. Four different can be produced limit, depending convergence ∂Ω. In one particular case, we obtain ‘strange’ condition featuring microscopic energy term related shape approaching domains. Many aspects our analysis could generalised an arbitrary order elliptic differential 2m and more general