Higher virial coefficients of a unitary Fermi gas

Third- and higher-order quantum virial coefficients require the solution of the corresponding quantum many-body problem. Nevertheless, in an earlier paper [Phys. Rev. Lett. 108, 260402 (2012)PRLTAO0031-900710.1103/PhysRevLett.108.260402], we proposed that the higher-order cluster integrals of a dilute unitary fermionic gas may be approximated in terms of the two-body cluster together with an appropriate suppression factor. Although not exact, this ansatz gave a fair agreement up to fugacity z≈6 with the experimentally obtained equation of state. The objective of the present Brief Report is to give some physical arguments in favor of this ansatz.