Virial calculations forH↓in two and three dimensions

Properties of spin-polarized hydrogen (${\mathrm{H}}_{\mathrm{\downarrow }}$) gas at low densities in two and three dimensions are calculated with the use of a quantum virial expansion. These properties include the second virial coefficients, heat capacities, chemical potentials, and estimates of critical temperatures and densities for Bose-Einstein condensation in three dimensions and for a hypothetical superfluid transition in two dimensions. The scattering phase shifts used are based on a Kolos-Wolniewicz two-body potential. The classical virial expansion and the validity of effective-range theory are discussed.