Effect of nonzero temperature to non-condensed fraction of a homogeneous dilute weakly interacting Bose gas

This study aims to investigate the effect of nonzero temperature to the non-condensed fraction of a homogeneous repulsive weakly interacting Bose gas in region of sufficiently low temperature. Within improved Hartree-Fock approximation, the Cornwall-Jackiw-Tomboulis effective action approach shows that the thermal fluctuations make the non-condensed fraction increase as a second and fourth-order power law of temperature. Indeed, the effect of non-infinite size of the trap is also integrated. The result is compared with experimental data.