Quantum depletion is the fraction of particles outside a condensate orbital in a Bose-gas ground state. For the constant
orbital 
on a periodic cube, write 
. The depletion is 
. It can be positive even at
zero temperature because of interactions.
Quantum Depletion
See also
Bose-Einstein Condensation, Bose Gas, Ground State, Scattering LengthExplore with Wolfram|Alpha
References
Lieb, E. H.; Seiringer, R.; Solovej, J. P.; and Yngvason, J. The Mathematics of the Bose Gas and Its Condensation. Basel, Switzerland: Birkhäuser, 2005. https://doi.org/10.1007/b137508.Cite this as:
Weisstein, Eric W. "Quantum Depletion." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/QuantumDepletion.html