 Harmonic-trap critical-temperature prefactor

The ideal isotropic-trap transition scale is $T_0=\zeta (3{)}^{-1/3}(\hslash \omega /k_B)N^{1/3}$. The numerical prefactor $\zeta (3{)}^{-1/3}\simeq 0.9405$ follows from the Bose integral ${\int }_0^{\infty }{x}^2/(e^x-1)dx=2\zeta (3)$.