  The collective modes of a familiar two-dimensional one-component-plasma with
the repulsive logarithmic interaction between the particles are analysed using
the quasi-crystalline approximation (QCA) combined with the molecular dynamic
simulation of the equilibrium structural properties. It is found that the
dispersion curves in the strongly coupled regime are virtually independent of
the coupling strength. Arguments based on the excluded volume consideration for
the radial distribution function allow us to derive very simple expressions for
the dispersion relations, which show excellent agreement with the exact QCA
dispersion over the entire domain of wavelengths. Comparison with the results
of the conventional fluid analysis is performed and the difference is
explained.
