= Off-diagonal long-range order
{title2=ODLRO}
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= ODLRO
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For a homogeneous bosonic condensate, the one-body <density matrix> retains a nonzero long-distance component. More generally, macroscopic occupation is identified by an eigenvalue of that <density matrix> proportional to particle number. This gives a number-conserving description even when the one-point annihilation-field expectation vanishes. In a paired fermionic system the corresponding macroscopic order belongs to the two-particle <density matrix>, rather than an <electron> single-particle condensate.
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