SINGLE-PARTICLE PROPERTIES OF A 2-DIMENSIONAL FERMI-LIQUID AT FINITE FREQUENCIES AND TEMPERATURES

We review the leading momentum, frequency, and temperature dependences of the single-particle self-energy and the corresponding term in the entropy of a two-dimensional Fermi liquid (FL) with a free-particle sp ectrum. We calculate the corrections to these leading dependences for the paramagnon model and the electron gas and find that the leading de pendences are limited to regions of energy and temperature which decre ase with decreasing number density of fermions. This can make it diffi cult to identify the frequency- and temperature-dependent characterist ics of a FL ground state in experimental quantities in low-density sys tems even when complications of band structure and other degrees of fr eedom are absent. This is an important consideration when the normal-s tate properties of the undoped cuprate superconductors are analyzed.