Quantum SDW liquid state originating from 2D electronic topological transition as a source for anomalies in the high-Tc cuprates

A new microscopic scenario for high Tc cuprates based on the existence of an electronic topological transition (ETT) in a strongly correlated 2D electron system has been developed recently. We first briefly sketch the principal results concerning the behaviour of a 2D fermion system on a square lattice close to an ETT and the main consequences for a strongly correlated system: d-wave superconductivity and SDW (CDW) quantum liquid state above TSC. We then illustrate how this theory can explain several crucial experimental facts (observed by NMR, angle resolved photoemission spectroscopy (ARPES), tunneling spectroscopy, inelastic neutron scattering) which reveal anomalous behavior in the SC state and in the metallic state above Tsc. (orig.)