Roma Tre University

About: Roma Tre University is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 4434 authors who have published 15352 publications receiving 374888 citations. The organization is also known as: Universita degli Studi Roma Tre & RomaTre.

Nonperturbatively improved heavy - light mesons: Masses and decay constants

Abstract: We present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved clover lattice action at $\ensuremath{\beta}=6.2,$ with a sample of $100$ configurations, on a ${24}^{3}\ifmmode\times\else\texttimes\fi{}64$ lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find ${f}_{{D}_{s}}=231\ifmmode\pm\else\textpm\fi{}{12}_{\ensuremath{-}1}^{+8} \mathrm{MeV},$ ${f}_{D}=211\ifmmode\pm\else\textpm\fi{}{14}_{\ensuremath{-}12}^{+2} \mathrm{MeV},$ ${f}_{{D}_{s}}{/f}_{D}=1.10(2),$ ${f}_{{B}_{s}}=204\ifmmode\pm\else\textpm\fi{}{16}_{\ensuremath{-}0}^{+36} \mathrm{MeV},$ ${f}_{B}=179\ifmmode\pm\else\textpm\fi{}{18}_{\ensuremath{-}9}^{+34} \mathrm{MeV},$ ${f}_{{B}_{s}}{/f}_{B}{=1.14(3)}_{\ensuremath{-}1}^{+1}.$ Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing a, support a large value of ${f}_{B}$ in the quenched approximation.

Tectonomagmatic characteristics of the back‐arc portion of the Calama–Olacapato–El Toro Fault Zone, Central Andes

Abstract: [1] Post–20 Ma magmatism in the Central Andes is either localized in the magmatic arc or distributed east of it, on the Altiplano-Puna Plateau. Here there is a distinct concentration of magmatic centers on NW–SE trending lineaments, such as the Calama–Olacapato–El Toro (COT), that extends into the Eastern Cordillera to the east of the Puna. Understanding the possible genetic relationship between prominent structures and magmatic centers on these lineaments is important to elucidate the tectonomagmatic evolution of the Central Andes. We investigated the back-arc area of the COT using remote sensing, geological, structural, and petrochemical data. Our study demonstrates that this portion of the COT consists of NW–SE striking faults, formed under overall left-lateral transtension that decreases in activity toward the COT termini. Deformation on the COT occurred during and after activity of prominent N–S striking transpressive fault systems and is coeval with magmatism, which is focused on the central COT. The most evolved magmatic rocks, with an upper crustal imprint, are exposed on the central COT, whereas more primitive, mantle-derived mafic to moderately evolved magmatic rocks, are found toward the COT termini. This points to a genetic relationship between upper crustal deformation and magmatic activity that led to enhanced magma storage in the central COT. COT magmas may result either from slab steepening or episodic delamination of the asthenospheric mantle.

Mantle cloaking for co-site radio-frequency antennas

Abstract: We show that properly designed mantle cloaks, consisting of patterned metallic sheets placed around cylindrical monopoles, allow tightly packing the same antennas together in a highly dense telecommunication platform. Our experimental demonstration is applied to the relevant example of two cylindrical monopole radiators operating for 3G and 4G mobile communications. The two antennas are placed in close proximity, separated by 1/10 of the shorter operational wavelength, and, after cloaking, are shown to remarkably operate as if isolated in free-space. This result paves the way to unprecedented co-siting strategies for multiple antennas handling different services and installed in overcrowded platforms, such as communication towers, satellite payloads, aircrafts, or ship trees. More broadly, this work presents a significant application of cloaking technology to improve the efficiency of modern communication systems.

The contribution of faint active galactic nuclei to the hard X-ray background

Abstract: Hard X-ray selection is the most efficient way to discriminate between accretion-powered sources, such as active galactic nuclei (AGN), and sources dominated by starlight. Hard X-rays are also less affected than other bands by obscuration. We have therefore carried out the BeppoSAX High Energy Large Area Survey (HELLAS) in the largely unexplored 5–10 keV band, finding 180 sources in ∼50 deg2 of sky with flux≳5×10−14 erg cm−2 s−1. After correction for the non-uniform sky coverage this corresponds to resolving about 30 per cent of the hard cosmic X-ray background (XRB). Here we report on a first optical spectroscopic identification campaign, finding 12 AGN out of 14 X-ray error boxes studied. Seven AGN show evidence for obscuration in X-ray and optical bands, a fraction higher than in previous ROSAT or ASCA–ROSAT surveys (at 95–99 and 90 per cent confidence levels respectively), thus supporting the scenario in which a significant fraction of the XRB is created by obscured AGN.

Geophysical investigations of habitability in ice-covered ocean worlds

Abstract: Geophysical measurements can reveal the structures and thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. We explore the variability and correlation of these parameters using 1-D internal structure models. We invoke thermodynamic consistency using available thermodynamics of aqueous MgSO_4, NaCl (as seawater), and NH_3; pure water ice phases I, II, III, V, and VI; silicates; and any metallic core that may be present. Model results suggest, for Europa, that combinations of geophysical parameters might be used to distinguish an oxidized ocean dominated by MgSO_4 from a more reduced ocean dominated by NaCl. In contrast with Jupiter's icy ocean moons, Titan and Enceladus have low-density rocky interiors, with minimal or no metallic core. The low-density rocky core of Enceladus may comprise hydrated minerals or anhydrous minerals with high porosity. Cassini gravity data for Titan indicate a high tidal potential Love number (k_2 > 0.6), which requires a dense internal ocean (ρ_(ocean) >1,200 kg m^(−3)) and icy lithosphere thinner than 100 km. In that case, Titan may have little or no high-pressure ice, or a surprisingly deep water-rock interface more than 500 km below the surface, covered only by ice VI. Ganymede's water-rock interface is the deepest among known ocean worlds, at around 800 km. Its ocean may contain multiple phases of high-pressure ice, which will become buoyant if the ocean is sufficiently salty. Callisto's interior structure may be intermediate to those of Titan and Europa, with a water-rock interface 250 km below the surface covered by ice V but not ice VI.