Evidence of electron fractionalization in the Hall coefficient at Mott criticality

Hall coefficient implies the mechanism for reconstruction of a Fermi surface, distinguishing competing scenarios for Mott criticality such as electron fractionalization, dynamical mean-field theory, and metal-insulator transition driven by symmetry breaking. We find that electron fractionalization leaves a signature for the Hall coefficient at Mott criticality in two dimensions, a unique feature differentiated from other theories. We evaluate the Hall coefficient based on the quantum Boltzman equation approach, guaranteeing gauge invariance in both longitudinal and transverse transport coefficients

Deep ROSAT-HRI observation of the elliptical galaxy NGC 1399

We present the preliminary results of a deep (167 ks) ROSAT HRI observation of the cD galaxy NGC1399 in the Fornax cluster. We find, in agreement with previous observations, an extended (41 Kpc adopting a distance of 19 Mpc) gaseous halo with a luminosity of L_X=(4.41\pm 0.04)x10^{41} erg/s. The 5 arcsec resolution of the data allows us to detect a very complex and asymmetric structure of the halo with respect to the optical galaxy. Moreover the analysis of the radial structure reveals the presence of a multi-component profile not consistent with a simple King model over the whole 40 Kpc. We do not detect the presence of a central source and pose an upper limit to the luminosity of a possible active nucleus. Due to the length of the observation, comparable to that of a deep survey, we detect a large number of sources within the HRI FOV, in slight excess with respect to the estimates based on previous surveys. We study the flux distribution of the sources, their temporal behaviour and their spatial distribution with respect to the central galaxy.Comment: 15 pages, 10 figures (6 in color), 1 table; uses subfigure.sty, supertabular.sty, lscape.sty, color.sty; To be published in the proceeding of "X-ray Astronomy 2000" (Mondello (Palermo), September 2000