Energy spectrum and optical absorption spectra of fullerene С$_{26}$ within the Hubbard model

Anticommutator Green's functions and energy spectra of fullerene С$_{26}$ and endohedral fullerene U@С$_{26}$ with the D$_{3h}$ symmetry groups have been obtained in an analytical form within the Hubbard model and static fluctuation approximation. The energy states have been classified using the methods of group theory, and the allowed transitions in the energy spectra of molecules С$_{26}$ and U@С$_{26}$ with the D$_{3h}$ symmetry groups have been determined.