Bulges

We model the evolution of the galactic bulge and of the bulges of a selected sample of external spiral galaxies, via the multiphase multizone evolution model. We address a few questions concerning the role of the bulges within galactic evolution schemes and the properties of bulge stellar populations. We provide solutions to the problems of chemical abundances and spectral indices, the two main observational constraints to bulge structure.Comment: 15 pages, 10 figures, to be published in MNRA

Filosofia e letteratura degli spazi naturali e umani: prove di dialogo interdisciplinare con Theo D\u2019haen

Studio sull\u2019interconnessione artistica tra spazio e tempo, su come ciascuno influenzi l\u2019altro nei lavori presi in esame dal Prof. D\u2019haen, e come lo spazio geografico diventi anche spazio culturale, in cui i personaggi arrivano a modificare la propria indole

Noise in Bose Josephson junctions: Decoherence and phase relaxation

Squeezed states and macroscopic superpositions of coherent states have been predicted to be generated dynamically in Bose Josephson junctions. We solve exactly the quantum dynamics of such a junction in the presence of a classical noise coupled to the population-imbalance number operator (phase noise), accounting for, for example, the experimentally relevant fluctuations of the magnetic field. We calculate the correction to the decay of the visibility induced by the noise in the non-Markovian regime. Furthermore, we predict that such a noise induces an anomalous rate of decoherence among the components of the macroscopic superpositions, which is independent of the total number of atoms, leading to potential interferometric applications.Comment: Fig 2 added; version accepted for publicatio

Oxygen and nitrogen abundances in Virgo and field spirals

The oxygen and nitrogen abundances in the HII regions of the nine Virgo spirals of the sample from Skillman et al (1996) and in nine field spiral galaxies are re-determined with the recently suggested P - method. We confirm that there is an abundance segregation in the sample of Virgo spirals in the sense that the HI deficient Virgo spirals near the core of the cluster have higher oxygen abundances in comparison to the spirals at the periphery of the Virgo cluster. At the same time both the Virgo periphery and core spirals have counterparts among field spirals. We conclude that if there is a difference in the abundance properties of the Virgo and field spirals, this difference appears to be small and masked by the observational errors.Comment: 16 pages, 10 figures, accepted for publication in Astronomy and Astrophysic

Effect of phase noise on useful quantum correlations in Bose Josephson junctions

In a two-mode Bose Josephson junction the dynamics induced by a sudden quench of the tunnel amplitude leads to the periodic formation of entangled states. For instance, squeezed states are formed at short times and macroscopic superpositions of phase states at later times. The two modes of the junction can be viewed as the two arms of an interferometer; use of entangled states allows to perform atom interferometry beyond the classical limit. Decoherence due to the presence of noise degrades the quantum correlations between the atoms, thus reducing phase sensitivity of the interferometer. We consider the noise induced by stochastic fluctuations of the energies of the two modes of the junction. We analyze its effect on squeezed states and macroscopic superpositions and study quantitatively the amount of quantum correlations which can be used to enhance the phase sensitivity with respect to the classical limit. To this aim we compute the squeezing parameter and the quantum Fisher information during the quenched dynamics. For moderate noise intensities we show that these useful quantum correlations increase on time scales beyond the squeezing regime. This suggests multicomponent superpositions as interesting candidates for high-precision atom interferometry

Ab-initio calculation of all-optical time-resolved calorimetry of nanosized systems: Evidence of nanosecond-decoupling of electron and phonon temperatures

The thermal dynamics induced by ultrashort laser pulses in nanoscale systems, i.e. all-optical time-resolved nanocalorimetry is theoretically investigated from 300 to 1.5 K. We report ab-initio calculations describing the temperature dependence of the electron-phonon interactions for Cu nanodisks supported on Si. The electrons and phonons temperatures are found to decouple on the ns time scale at 10 K, which is two orders of magnitude in excess with respect to that found for standard low-temperature transport experiments. By accounting for the physics behind our results we suggest an alternative route for overhauling the present knowledge of the electron-phonon decoupling mechanism in nanoscale systems by replacing the mK temperature requirements of conventional experiments with experiments in the time-domain.Comment: 5 pages, 3 figures. Accepted on Physical Review B

Characterizing stellar populations in spiral disks

It is now possible to measure detailed spectral indices for stellar populations in spiral disks. We propose to interpret these data using evolutionary synthesis models computed from the Star Formation Histories obtained from chemical evolutionary models. We find that this technique is a powerful tool to discriminate between old and young stellar populations. We show an example of the power of Integral Field spectroscopy in unveiling the spatial distribution of populations in a barred galaxy.Comment: 5 pages, to be published in "Science Perspectives for 3D Spectroscopy", Eds. M. Kissler-Patig, M.M. Roth and J.R. Walsh (Springer-Verlag, ESO astrophysics symposia series

Eco-friendly gas mixtures for Resistive Plate Chambers based on Tetrafluoropropene and Helium

Due to the recent restrictions deriving from the application of the Kyoto protocol, the main components of the gas mixtures presently used in the Resistive Plate Chambers systems of the LHC experiments will be most probably phased out of production in the coming years. Identifying possible replacements with the adequate characteristics requires an intense R&D, which was recently started, also in collaborations across the various experiments. Possible candidates have been proposed and are thoroughly investigated. Some tests on one of the most promising candidate - HFO-1234ze, an allotropic form of tetrafluoropropane- have already been reported. Here an innovative approach, based on the use of Helium, to solve the problems related to the too elevate operating voltage of HFO-1234ze based gas mixtures, is discussed and the relative first results are shown.Comment: 9 pages, 6 figures, 1 tabl