  The heirarchical mean-field theory of elastic networks, originally developed
by Maxwell to discuss the stability of scaffolds, and recently applied to
atomic networks by Phillips and Thorpe, explains the phase diagrams and
remarkable superconductive properties of cuprates as the result of giant
electron-phonon interactions in a marginally unstable mechanical network. The
overall cuprate networks are fragile (floppy), as shown quantitatively (with an
accuracy ~1 percent), and without adjustable parameters, by comparison with
stabilities of generically similar network glasses, and are stabilized by
percolative backbones composed of CuO2 planes.
