The longitudinal and transverse responses in the inclusive electron scattering: a functional approach

The splitting between the charge-longitudinal and spin-transverse responses is explained in a model whose inputs are the effective interactions in the particle-hole channels in the frame of the first order boson loop expansion. It is shown that the interplay between $\omega$-meson exchange and box diagrams (two-meson exchange with simultaneous excitation of one or two nucleons to $\Delta$'s) mainly rules the longitudinal response, while in the transverse one the direct $\Delta$ excitations almost cancel the one-loop correction and the response is mainly governed by the $\rho$-meson rescattering inside the nucleus. It is also shown that a small variation in the nuclear densities may explain the observed discrepancies between different nuclei.Comment: LaTex2e file with 53 .ps figures; submitted to Nucl. Phys

Functional approach to the electromagnetic response function: the Longitudinal Channel

In this paper we address the (charge) longitudinal electromagnetic response for a homogeneous system of nucleons interacting via meson exchanges in the functional framework. This approach warrants consistency if the calculation is carried on order-by-order in the mesonic loop expansion with RPA-dressed mesonic propagators. At the 1-loop order and considering pion, rho and omega exchanges we obtain a quenching of the response, in line with the experimental results.Comment: RevTeX, 18 figures available upon request - to be published in Physical Review

GPS-based monitoring of land subsidence in the Po Plain (Northern Italy)

We use regional and local networks of continuously-operating GPS stations (CGPS) distributed in the northern–central part of the Italian peninsula to investigate the subsidence phenomenon of the Po plain sedimentary basin and vertical movements of the surrounding areas. The observations of 146 scientific and commercial stations are analyzed and compared, adopting analytical techniques widely used to study GPS coordinate time series. The use of simple antenna supports in commercial installations, instead of a more rigorous geodetic monument, does not seem to induce significant differences in the noise characteristics and in the amplitudes of annual and semi-annual periodic signals. The vertical velocity field deduced from 129 sites with observation time spans greater than one year, located in the Central–Northern Italian Peninsula, indicates the presence of two mainly subsidence areas: the Po Plain and the Arno Plain, while the sites located in the Alps and Apennine domains show relatively low uplift. The areas of the Po Plain monitored by GPS seem to indicate that the subsidence rate is constant or, in some cases, decreasing with respect to the values obtained from the last measurements, performed up to 2006 by means of both SAR and levelling techniques. Only the central part of the eastern Po Plain close to the Apennine border (Modena city area) is characterized by a peak in subsidence consisting in a velocity of about 15 mm/yr