Genuine Tripartite Entanglement in a Spin-Star Network at Thermal Equilibrium

In a recent paper [M. Huber {\it et al}, Phys. Rev. Lett. {\bf 104}, 210501 (2010)] new criteria to find out the presence of multipartite entanglement have been given. We exploit these tools in order to study thermal entanglement in a spin-star network made of three peripheral spins interacting with a central one. Genuine tripartite entanglement is found in a wide range of the relevant parameters. A comparison between predictions based on the new criteria and on the tripartite negativity is also given.Comment: 8 pages, 13 figure

Heat Capacity and Entanglement Measure in a simple two-qubit model

A simple two-qubit model showing Quantum Phase Transitions as a consequence of ground state level crossings is studied in detail. Using the Concurrence of the system as an entanglement measure and heat capacity as a marker of thermodynamical properties, an analytical expression giving the latter in terms of the former is obtained. A protocol allowing an experimental measure of entanglement is then presented and compared with a related proposal recently reported by Wie\'sniak, Vedral and BruknerComment: 7 pages, 3 figure

Revealing non-classical behaviours in the oscillatory motion of a trapped ion

The possibility of revealing non-classical behaviours in the dynamics of a trapped ion via measurements of the mean value of suitable operators is reported. In particular we focus on the manifestation known as `` Parity Effect\rq\rq which may be observed \emph{directly measuring} the expectation value of an appropriate correlation operator. The experimental feasibility of our proposal is discussed.Comment: 5 pages, 2 figure

Quantum Phase Transitions and Heat Capacity in a two-atoms Bose-Hubbard Model

We show that a two-atoms Bose-Hubbard model exhibits three different phases in the behavior of thermal entanglement in its parameter space. These phases are demonstrated to be traceable back to the existence of quantum phase transitions in the same system. Significant similarities between the behaviors of thermal entanglement and heat capacity in the parameter space are brought to light thus allowing to interpret the occurrence and the meaning of all these three phases.Comment: 6 pages, 3 figure

Geometric phase accumulation-based effects in the quantum dynamics of an anisotropically trapped ion

New physical effects in the dynamics of an ion confined in an anisotropic two-dimensional Paul trap are reported. The link between the occurrence of such manifestations and the accumulation of geometric phase stemming from the intrinsic or controlled lack of symmetry in the trap is brought to light. The possibility of observing in laboratory these anisotropy-based phenomena is briefly discussed.Comment: 10 pages. Acta Physica Hungarica B 200

Zeno Dynamics and High-Temperature Master Equations Beyond Secular Approximation

Complete positivity of a class of maps generated by master equations derived beyond the secular approximation is discussed. The connection between such class of evolutions and physical properties of the system is analyzed in depth. It is also shown that under suitable hypotheses a Zeno dynamics can be induced because of the high temperature of the bath.Comment: 9 pages, 2 figure

Evidence from stellar rotation of enhanced disc dispersal: (I) The case of the triple visual system BD-21 1074 in the β\beta Pictoris association

The early stage of stellar evolution is characterized by a star-disc locking mechanism. The disc-locking prevents the star to spin its rotation up, and its timescale depends on the disc lifetime. Some mechanisms can significantly shorten this lifetime, allowing a few stars to start spinning up much earlier than other stars. In the present study, we aim to investigate how the properties of the circumstellar environment can shorten the disc lifetime. We have identified a few multiple stellar systems, composed of stars with similar masses, which belong to associations with a known age. Since all parameters that are responsible for the rotational evolution, with the exception of environment properties and initial stellar rotation, are similar for all components, we expect that significant differences among the rotation periods can only arise from differences in the disc lifetimes. A photometric timeseries allowed us to measure the rotation periods of each component, while high-resolution spectra provided us with the fundamental parameters, $v\sin{i}$ and chromospheric line fluxes. The rotation periods of the components differ significantly, and the component B, which has a closer companion C, rotates faster than the more distant and isolated component A. We can ascribe the rotation period difference to either different initial rotation periods or different disc-locking phases arising from the presence of the close companion C. In the specific case of BD$-$21 1074, the second scenario seems to be more favored. In our hypothesis of different disc-locking phase, any planet orbiting this star is likely formed very rapidly owing to a gravitational instability mechanism, rather than core accretion. Only a large difference of initial rotation periods alone could account for the observed period difference, leaving comparable disc lifetimes.Comment: Accepted by Astronomy & Astrophysics on July 31, 2014; Pages 12, Figs.

La coltivazione del grano tenero in Sicilia: prime valutazioni economiche

The Sicilian 2007-2013 Rural Development Program of Sicily, by the measure 1.2.3 "Enhance of the added value of agricultural and forestry products", created the conditions for the conclusion of supply contracts between a milling company and 18 Sicilian farmers who are committed to annually grow about 600 hectares of common wheat in 2010-2013. With reference to the years 2010-2012, a survey was conducted using data collected from 4 of the 18 grain farms involved in the initiative that have grown in this period both durum and common wheat, in order to quantify the key economic parameters and to allow an initial comparison. The evaluation showed interesting results for the common wheat both from the point of view of production (average yield of 47,7 q/ha), and in terms of the gross salable production (average 1.606 €/ha). The most significant economic parameters to evaluate the productive outcome, such as EBITDA and net, average resulted respectively 859 and 444 €/ha, about 100 €/ha more than what has been recorded for durum wheat; also the unit cost of production for the common wheat grain was significantly lower than that of durum wheat (-13%)