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.

The planetary N -body problem: symplectic foliation, reductions and invariant tori

Abstract: The 6n-dimensional phase space of the planetary (1+n)-body problem (after the classical reduction of the total linear momentum) is shown to be foliated by symplectic leaves of dimension (6n−2) invariant for the planetary Hamiltonian ${\mathcal{H}}$ . Such foliation is described by means of a new global set of Darboux coordinates related to a symplectic (partial) reduction of rotations. On each symplectic leaf ${\mathcal{H}}$ has the same form and it is shown to preserve classical symmetries. Further sets of Darboux coordinates may be introduced on the symplectic leaves so as to achieve a complete (total) reduction of rotations. Next, by explicit computations, it is shown that, in the reduced settings, certain degeneracies are removed. In particular, full torsion is checked both in the partially and totally reduced settings. As a consequence, a new direct proof of Arnold’s theorem (Arnold in Russ. Math. Surv. 18(6):85–191, 1963) on the stability of planetary system (both in the partially and in the totally reduced setting) is easily deduced, producing Diophantine Lagrangian invariant tori of dimension (3n−1) and (3n−2). Finally, elliptic lower dimensional tori bifurcating from the secular equilibrium are easily obtained.

Search for dilepton resonances in pp collisions at √s=7 TeV with the ATLAS detector.

Abstract: This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at root s = 7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb(-1) in the e(+)e(-) (mu(+)mu(-)) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C. L. on the cross section times branching fraction of Z' resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z' boson is set. A Randall-Sundrum graviton with coupling k/(M) over bar Pl = 0.1 is excluded at 95% C. L. for masses below 1.63 TeV.

Anatomy of the AGN in NGC 5548 - II. The spatial, temporal, and physical nature of the outflow from HST/COS Observations

Abstract: Context. AGN outflows are thought to influence the evolution of their host galaxies and of super massive black holes. Our deep multiwavelength campaign on NGC 5548 has revealed a new, unusually strong X-ray obscuration, accompanied by broad UV absorption troughs observed for the first time in this object. The X-ray obscuration caused a dramatic decrease in the incident ionizing flux on the outflow that produces the long-studied narrow UV absorption lines in this AGN. The resulting data allowed us to construct a comprehensive physical, spatial, and temporal picture for this enduring AGN wind. Aims. We aim to determine the distance of the narrow UV outflow components from the central source, their total column-density, and the mechanism responsible for their observed absorption variability. Methods. We study the UV spectra acquired during the campaign, as well as from four previous epochs (1998−2011). Our main analysis tools are ionic column-density extraction techniques, photoionization models based on the code CLOUDY, and collisional excitation simulations. Results. A simple model based on a fixed total column-density absorber, reacting to changes in ionizing illumination, matches the very different ionization states seen in five spectroscopic epochs spanning 16 years. The main component of the enduring outflow is situated at 3.5 ± 1.1 pc from the central source, and its distance and number density are similar to those of the narrow-emitting-line region in this object. Three other components are situated between 5−70 pc and two are farther than 100 pc. The wealth of observational constraints and the anti-correlation between the observed X-ray and UV flux in the 2002 and 2013 epochs make our physical model a leading contender for interpreting trough variability data of quasar outflows. Conclusions. This campaign, in combination with prior UV and X-ray data, yields the first simple model that can explain the physical characteristics and the substantial variability observed in an AGN outflow.

A federated architecture approach for Internet of Things security

Abstract: Internet of Things (IoT) refers to the capability to connect, communicate and remotely manage a large number of networked, automated devices via the Internet. IoT is becoming as part of daily life and aims to extend pervasive communication and networking anytime, anywhere with any device. In this context security requirements and architectures must be properly formulated, implemented in order to enforce the security policies during their life-cycle. This paper provides a survey and analysis of security in the area of IoT introducing an approach addressed to overcome the conventional security solutions and deploy a federated architecture for dynamic prevention, detection, diagnosis, isolation, and countermeasures against cyber attacks. Based on the analysis of the most common web services, the paper defines the security needs proposing a federated model to design an architecture for secure exchange of services in IoT paradigm.