Question

$\mathrm{i}\epsilon$ prescription makes a function analytical?

Answer 1

We propose a microscopic justification for the recently proposed “marginal Fermi-liquid” (MFL) phenomenology of the high Tc materials. In some models, and for sufficiently strong interactions, excitonic charge and spin modes between quasi-coherent one-particle states at the chemical potential and high-energy incoherent one-particle states which are the residual of the Hubbard bands of the insulating phase gives rise to singularities in certain low energy scattering amplitudes. The resulting new phase has the MFL polarizabilities. The one-particle spectrum near the chemical contribution.