Feasibility of approximating spatial and local entanglement in long-range interacting systems using the extended Hubbard model

We investigate the extended Hubbard model as an approximation to the local and spatial entanglement of a one-dimensional chain of nanostructures where the particles interact via a long range interaction represented by a `soft' Coulomb potential. In the process we design a protocol to calculate the particle-particle spatial entanglement for the Hubbard model and show that, in striking contrast with the loss of spatial degrees of freedom, the predictions are reasonably accurate. We also compare results for the local entanglement with previous results found using a contact interaction (PRA, 81 (2010) 052321) and show that while the extended Hubbard model recovers a better agreement with the entanglement of a long-range interacting system, there remain realistic parameter regions where it fails to predict the quantitative and qualitative behaviour of the entanglement in the nanostructure system.Comment: 6 pages, 5 figures and 1 table; added results with correlated hopping term; accepted by EP

Intersubband spin-orbit coupling and spin splitting in symmetric quantum wells

In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to the well-known Dresselhaus and Rashba effects. If one considers quantum wells with two or more conduction subbands, an additional, intersubband-induced spin-orbit term appears whose strength is comparable to the Rashba coupling, and which remains finite for symmetric structures. We show that the conduction band spin splitting due to this intersubband spin-orbit coupling term is negligible for typical III-V quantum wells

Telescope performance and image simulations of the balloon-borne coded-mask protoMIRAX experiment

In this work we present the results of imaging simulations performed with the help of the GEANT4 package for the protoMIRAX hard X-ray balloon experiment. The instrumental background was simulated taking into account the various radiation components and their angular dependence, as well as a detailed mass model of the experiment. We modeled the meridian transits of the Crab Nebula and the Galatic Centre region during balloon flights in Brazil ($\sim -23^{\circ}$ of latitude and an altitude of $\sim 40 \thinspace$ km) and introduced the correspondent spectra as inputs to the imaging simulations. We present images of the Crab and of three sources in the Galactic Centre region: 1E 1740.7-2942, GRS 1758-258 and GX 1+4. The results show that the protoMIRAX experiment is capable of making spectral and timing observations of bright hard X-ray sources as well as important imaging demonstrations that will contribute to the design of the MIRAX satellite mission.Comment: 9 figure

Search for an infrared counterpart of IGR J16358-4756

We report here on near infrared observations of the field around IGR J16358-4756. The source belongs to the new class of highly absorbed X-ray binaries discovered by IBIS/INTEGRAL. Our primary goal was to identify the infrared counterpart of the source, previously suggested to be a LMXB and then further reclassified as a HMXB. We have made use of Chandra observations of the source in order to better constrain the number of possible counterparts. Using the differential photometry technique, in observations spanning a timescale of 1 month, we found no long term variability in our observations. This is compatible, and we suggest here, that the source is a HMXB.Comment: 5 pages, 2 figures, all styles included; to be published in: "The Transient Milky Way: a perspective for MIRAX", eds. F. D'Amico, J. Braga, and R. E. Rothschild, AIP Conference Proceeding

Codice per il calcolo della pericolosità sismica da dati di sito: SASHA (Site Approach to Seismic Hazard Assessment)

Viene presentato il codice di calcolo SASHA che implementa l’approccio probabilistico proposto da Albarello e Mucciarelli (2002) alla stima della pericolosità sismica in termini di intensità macrosismica. Elemento chiave della metodologia è la storia sismica locale, ovvero i risentimenti documentati al sito dei terremoti passati eventualmente integrati da risentimenti “virtuali” dedotti a partire da dati epicentrali. La procedura (approccio “di sito”), appositamente sviluppata per l’analisi di dati di intensità, consente di utilizzare in modo formalmente corretto la grande quantità di informazioni macrosismiche disponibili in paesi come l’Italia. Oltre al presente testo, nel quale è descritto in dettaglio l’utilizzo del programma (metodologia, opzioni di calcolo, formato dei file di input/output), vengono allegati l’eseguibile di SASHA e un esempio dei file di input (catalogo epicentrale e dei risentimenti macrosismici, elenco di località) e output

Local magnitude estimate at Mt. Etna

In order to verify the duration magnitude MD we calculated local magnitude ML values of 288 earthquakes occurring from October 2002 to April 2003 at Mt. Etna. The analysis was computed at three digital stations of the permanent seismic network of Istituto Nazionale di Geofisica e Vulcanologia of Catania, using the relationship ML = logA+alog?-b, where A is maximum half-amplitude of the horizontal component of the seismic recording measured in mm and the term «+alog?-b» takes the place of the term «-logA0» of Richter relationship. In particular, a = 0.15 for ?<200 km, b=0.16 for ?<200 km. Duration magnitude MD values, moment magnitude MW values and other local magnitude values were compared. Differences between ML and MD were obtained for the strong seismic swarms occurring on October 27, during the onset of 2002-2003 Mt. Etna eruption, characterized by a high earthquake rate, with very strong events (seismogram results clipped in amplitude on drum recorder trace) and high level of volcanic tremor, which not permit us to estimate the duration of the earthquakes correctly. ML and MD relationships were related and therefore a new relationship for MD is proposed. Cumulative strain release calculated after the eruption using ML values is about 1.75E+06 J1/2 higher than the one calculated using MD values

Synergetical use of analytical models and machine-learning for data transport abstraction in open optical networks

The key-operation to enabling an effective data transport abstraction in open optical line systems (OLS) is the capability to predict the quality of transmission (QoT), that is given by the generalized signal-to-noise ratio (GSNR), including both the effects of the ASE noise and the nonlinear interference (NLI) accumulation. Among the two impairing effects, the estimation of the ASE noise is the most challenging task, because of the spectrally resolved working point of the erbium-doped fiber amplifiers (EDFA) depending on the spectral load, given the overall gain. While, the computation of the NLI is well addressed by mathematical models based on the knowledge of parameters and spectral load of fiber spans. So, the NLI prediction is mainly impaired by the uncertainties on insertion losses an spectral tilting. An accurate and spectrally resolved GSNR estimation enables to optimize the power control and to reliably and automatically deploy lightpaths with minimum margin, consequently maximizing the transmission capacity. We address the potentialities of machine-learning (ML) methods combined with analytic models for the NLI computation to improve the accuracy in the QoT estimation. We also analyze an experimental data-set showing the main uncertainties and addressing the use of ML to predict their effect on the QoT estimation

A scoring test on probabilistic seismic hazard estimates in Italy

"Probabilistic estimates of seismic hazard represent a basic element for seismic risk reduction strategies and they are a key element of seismic regulation. Thus, it is important to select the most effective estimates among the available ones. An empirical scoring strategy is described here and is applied to a number of time-independent hazard estimates available in Italy both at national and regional scale. The scoring test is based on the comparison of outcomes provided by available computational models at a number of accelero-metric sites where observations are available for 25 years. This comparison also allows identifying computational models that, providing outcomes that are in contrast with observations, should thus be discarded. The analysis shows that most of the hazard estimates proposed for Italy are not in contrast with observations and some computational models perform significantly better than others do. Furthermore, one can see that, at least locally, older estimates can perform better than the most recent ones. Finally, since the same computational model can perform differently depending on the region considered and on average return time of concern, no single model can be considered as the best-performing one. This implies that, moving along the hazard curve, the most suitable model should be selected by considering the specific problem of concern.