# What is the fluid approximation for BCS action?

For a system with free fermion gas at finite density (i.e. free Dirac action), we have an ideal fluid description with rho, p, n. What is the fluid description for BCS action? Suppose we have a box of Fermi gas, the fermions have BCS type interaction, what is the equation of state? what is rho,p, n etc? Any ref on this? THanks!

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