Polarization Effects on Three-Particle Correlation Energy in a Fermion System of Hard Spheres

The three-particle correlation energy induced by the polarization effects in the ground state system of hard core fermions is studied with the aid of an effective potential which prevents the cores from penetrating each other. The energy varies as a^4 log a with the small value of the core radius a and is not analytic at a = O. The nonanalyticity is responsible for the failure of the linked cluster expansion formalism, complemented with the partial summation method, in giving a finite value to the three-particle correlation energy in quantum fluid. It shows that t, he expansion of the energy beyond third order terms in t, he coupling const, ant, is not possible. The energy is examined more carefully and components behaving as a^4 are identified. Nonanalyitic component besides the a^4 log a term and dominating the a^4 term, such as a^4 log |log a|, is not found