Cooper problem
= Cooper problem
{c}
Two added <electrons> move above a frozen filled <Fermi sea> and attract within a thin <energy> shell. The Pauli-blocked continuum has a logarithmic pair susceptibility, so an arbitrarily weak net attractive constant interaction produces a state below the two-particle threshold at zero <temperature>. This two-added-particle result is not by itself a full many-electron superconducting state.