Normal-mode theory for cylinder arrays

We study a set of interacting cylinders under the influence of an electroma gnetic field in the long-wavelength limit. Cylindrical harmonics are used a s basis functions in order to write the electric potential in terms of mult ipolar moments of the charge distribution in the cylinders. We get a normal -mode expansion where the effects of geometry and material are separated. I t is shown that for a row of identical parallel cylinders the electromagnet ic modes are distributed symmetrically about the depolarization factor 1/2, each set coupling to different components of the external field. The ampli tudes of these symmetric depolarization factors are the same and satisfy pr oper sum rules.