Theories of High Temperature Superconductivity

While the theory of low temperature superconductors has been well established for more than two decades, the theory of the high temperature cuprates has yet to be agreed upon. Several of the leading proposals will be discussed, including spin fluctuations, interlayer tunneling, phase fluctuations of the order parameter, and excitations in short coherence length materials. The essential physical ideas will be stressed. These materials will depend upon high and ultra high magnetic fields to judge which theory is correct.