= Condensate density
{title2=$n_0=N_0/V$}
For a homogeneous gas, the condensate density is the macroscopic occupation $N_0$ of its condensate mode divided by volume. More generally its spatial density is $N_0|\varphi_0(x)|^2$ for a normalized condensate orbital. The mode and occupation are defined by a macroscopic eigenvalue of the one-body density matrix, so a finite fixed-number state need not have a nonzero field expectation. Condensate density is distinct from the superfluid density defined by response to a phase twist; interactions can deplete the former even when the latter equals the total density at zero temperature in a uniform Galilean-invariant gas.
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