Evidence for Deviations from Fermi-Liquid Behaviour in (2+1)-Dimensional Quantum Electrodynamics and the Normal Phase of High-$T_c$ Superconductors

We provide evidence that the gauge-fermion interaction in multiflavour quantum electrodynamics in $(2 + 1)$-dimensions is responsible for non-fermi liquid behaviour in the infrared, in the sense of leading to the existence of a non-trivial (quasi) fixed point (cross-over) that lies between the trivial fixed point (at infinite momenta) and the region where dynamical symmetry breaking and mass generation occurs. This quasi-fixed point structure implies slowly varying, rather than fixed, couplings in the intermediate regime of momenta, a situation which resembles that of (four-dimensional) `walking technicolour models of particle physics. Connection with the anomalous normal-state properties of certain condensed matter systems relevant for high-temperature superconductivity is briefly discussed. The relevance of the large (flavour) N expansion to the fermi-liquid problem is emphasized.