When the integral (also known as Bose–Einstein integral) is evaluated with factors of k B and ℏ restored by dimensional analysis, it gives the critical temperature formula of the preceding section. Therefore, this integral defines the critical temperature and particle number corresponding to the conditions of negligible chemical potential μ μ . In Bose–Einstein statistics distribution, μ μ is actually still nonzero for BECs; however, μ μ is less than the ground state energy. Except when specifically talking about the ground state, μ μ can be approximated for most energy or momentum states as μ μ ≈ ≈ 0 .