One-click electromagnetism at the nanoscale
A sphere with an inclusion that is not centred: a core displaced inside its shell, as often happens in real core–shell synthesis. The calculator solves it exactly with re-expanded multipoles.
Displacing the core breaks the symmetry: modes that cannot be excited in a concentric particle become visible, resonances shift and split, and the field concentrates where the shell is thinnest.
Yes: put the inclusion at the centre to recover the concentric core–shell result, then move it to see the effect.
An off-centre core inside a shell: fields and resonances from an exact multipole solution.