Spectral stability under removal of small capacity sets and applications   to Aharonov-Bohm operators
  We first establish a sharp relation between the order of vanishing of a Dirichlet eigenfunction at a point and the leading term of the asymptotic expansion of the Dirichlet eigenvalue variation, as a removed compact set concentrates at that point. Then we apply this spectral stability result to the study of the asymptotic behaviour of eigenvalues of Aharonov-Bohm operators with two colliding poles moving on an axis of symmetry of the domain. 
Laura Abatangelo, Veronica Felli, Luc Hillairet, Corentin Lena
math.AP