Study on the some logarithmic contributions approximately α6lnα to hyperfine ground state splitting in positronium

A quasipotential for two-particle interaction in positronium is built up. Quasipotential elements correspond to the Feynman diagrams in high-frequency region, whereas in low frequency region it is being built with the help of he Coulomb Green function. On the basis of the quasipotential approach studied are some additional contributions of the α6lnα order into the hyperfine splitting of the main positronium level. The approach gives the effective and successive method of finding out the corrections of highest orders for energy levels of bound states