Axisymmetric equilibrium models for magnetized neutron stars in General Relativity under the Conformally Flat Condition

Extremely magnetized neutron stars with magnetic fields as strong as $\sim 10^{15-16}$ G, or magnetars, have received considerable attention in the last decade due to their identification as a plausible source for Soft Gamma Repeaters and Anomalous X-ray Pulsars. Moreover, this class of compact objects has been proposed as a possible engine capable of powering both Long and Short Gamma-Ray Bursts, if the rotation period in their formation stage is short enough (~1 ms). Such strong fields are expected to induce substantial deformations of the star and thus to produce the emission of gravitational waves. Here we investigate, by means of numerical modeling, axisymmetric static equilibria of polytropic and strongly magnetized stars in full general relativity, within the ideal magneto-hydrodynamic regime. The eXtended Conformally Flat Condition (XCFC) for the metric is assumed, allowing us to employ the techniques introduced for the X-ECHO code [Bucciantini & Del Zanna, 2011, Astron. Astrophys. 528, A101], proven to be accurate, efficient, and stable. The updated XNS code for magnetized neutron star equilibria is made publicly available for the community (see www.arcetri.astro.it/science/ahead/XNS). Several sequences of models are here retrieved, from the purely toroidal (resolving a controversy in the literature) or poloidal cases, to the so-called twisted torus mixed configurations, expected to be dynamically stable, which are solved for the first time in the non-perturbative regime.Comment: 24 pages, 22 figures, 5 table

On the Semantic of Ageing: from Successful Ageing to Dynamic and Developmental Model of Ageing

During the second part of Twentieth Century worldwide there has been an important process of conceptualization on active ageing and healthy ageing, related to the progressive ageing of population in most of the countries, the so called “Demographic revolution” or “Demographic transition” (Rowe e Kahn, 1987, 1988, 1998, Bates and Bates, 1990, 1993, Kahn, 2002, 2004, Pruchno et al., 2010, Petretto et al., 2016a). We can divide the conceptualization in different groups: American conceptual models, European conceptual models and other conceptual models related to different points of view on ageing (Fernandez-Ballesteros et al., 2011a e b, . The conceptualization of ageing is strictly related to the anthropological framework at the bottom of it and to the interest to all phases of the life, but it is also strictly related to semantical choices at the bottom of the conceptual models (Petretto et al., 2016). In the semantic of ageing we found different words, like active ageing, healthy ageing, and successful ageing and so on. There are different variables that make the difference: a focus on subject and subjectivity, a focus on well-being and quality of life as central outcomes, and on the sociocultural influences that make some variables more important than others and define the role of oldest people in the society. The aim of paper is to discuss different variables related to different semantical choices and to propose some critical hints of analysis in this field

General relativistic models for rotating magnetized neutron stars in conformally flat spacetime

The extraordinary energetic activity of magnetars is usually explained in terms of dissipation of a huge internal magnetic field of the order of $10^{15-16}$G. How such a strong magnetic field can originate during the formation of a neutron star is still subject of active research. An important role can be played by fast rotation: if magnetars are born as millisecond rotators dynamo mechanisms may efficiently amplify the magnetic field inherited from the progenitor star during the collapse. In this case, the combination of rapid rotation and strong magnetic field determine the right physical condition not only for the development of a powerful jet driven explosion, manifesting as a gamma ray burst, but also for a copious gravitational waves emission. Strong magnetic fields are indeed able to induce substantial quadrupolar deformations in the star. In this paper we analyze the joint effect of rotation and magnetization on the structure of a polytropic and axisymmetric neutron star, within the ideal magneto-hydrodynamic regime. We will consider either purely toroidal or purely poloidal magnetic field geometries. Through the sampling of a large parameter space, we generalize previous results in literature, inferring new quantitative relations that allow for a parametrization of the induced deformation, that takes into account also the effects due to the stellar compactness and the current distribution. Finally, in the case of purely poloidal field, we also discuss how different prescriptions on the surface charge distribution (a gauge freedom) modify the properties of the surrounding electrosphere and its physical implications.Comment: 25 pages, 17 figures, 6 tables, accepted for publication in MNRA

Multiple scattering measurements in laboratory and foggy atmosphere

Multiple scattering affects propagation of light beams in turbid media. Backscattering or forward scattering based measurements of atmospheric parameters are influenced by this effect. Although largely studied theoretically, the effect needs measurements in control of situations due to the large variety of situations of practical importance. The results of laboratory measurements pertaining to the transmission of a collimated light beam (Helium-Neon souce, 10 mW) through suspensions of latex spheres in water are presented and a comparison was made with the predictions of calculation in a foggy atmosphere will also be presented

Photo-realistic image synthesis in volume rendering for rapid prototyping and CAM applications (draft)

This document describes some preliminary results of the application of direct volume visualization and realistic image synthesis techniques in Computer Aided Manufacturing (CAM) field. The final goal is to analyze the use volume data representation and direct volume visualization techniques respectively as basic geometric element and rendering method for numerical control (NC) process planning and simulation. In particular we want to study their application in the process of human organs replication by rapid prototyping techniques. Volume rendering techniques will be used to evaluate the geometric reconstruction of volumetric data (e.g. parts of human body extracted from a CT scan as the carotid arteries), in order to obtain the best polygonal approximation of a dataset. The polygonal model resulting from this evaluation stage will be used to drive its physical reconstruction via rapid prototyping. A volume rendering program, called VolCastIA, is presented. VolCastIA is a software environment built to evaluate the use of state of the art image synthesis methods in the volume rendering context