BREAKDOWN OF THE FERMI-LIQUID PICTURE IN ONE-DIMENSIONAL FERMION SYSTEMS - CONNECTION WITH THE ENERGY-LEVEL STATISTICS

Using the adiabatic switching of interactions, we establish a conditio n for the existence of electronic quasiparticles in a Luttinger liquid . It involves a characteristic interaction strength proportional to th e inverse square root of the system length. An investigation of the ex act energy level separation probability distribution shows that this i nteraction scale also corresponds to a cross-over from the non interac ting behaviour to a rather typical case for integrable systems, namely an exponential distribution. The level spacing statistics of a spin 1 /2, one branch Luttinger model are also analyzed, as well as the level statistics of a two coupled chain model.