Bethe ansatz approach to the pairing fluctuations in the mesoscopic regime (Q2897053)

The current understanding of the mesoscopic fluctuations of the pairing instability based on the Bethe ansatz is reviewed. The key for the calculations was provided by relating the discrete BCS model to known integrable theories corresponding to the so-called Gaudin magnets with suitable boundary terms. The relevant quantity is a correlation function, where the physical observables are evaluated as a static expectation value in the eigenstates of the Hamiltonian. The progress in the field of exact integrable systems allows an exhaustive analysis of superconductivity from mesoscopic regimes to the thermodynamic limit at equilibrium.