5,756 research outputs found

    On the characterization of isotropic Gaussian fields on homogeneous spaces of compact groups

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    Let T be a random field invariant under the action of a compact group G We give conditions ensuring that independence of the random Fourier coefficients is equivalent to Gaussianity. As a consequence, in general it is not possible to simulate a non-Gaussian invariant random field through its Fourier expansion using independent coefficients

    The effect of supersymmetry breaking in the Mass Varying Neutrinos

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    We discuss the effect of the supersymmetry breaking on the Mass Varying Neutrinos(MaVaNs) scenario. Especially, the effect mediated by the gravitational interaction between the hidden sector and the dark energy sector is studied. A model including a chiral superfield in the dark sector and the right handed neutrino superfield is proposed. Evolutions of the neutrino mass and the equation of state parameter are presented in the model. It is remarked that only the mass of a sterile neutrino is variable in the case of the vanishing mixing between the left-handed and a sterile neutrino on cosmological time scale. The finite mixing makes the mass of the left-handed neutrino variable.Comment: 6 pages, 7 figures, RevTeX4, references added, discussions and figures revise

    The evolution of the spatially-resolved metal abundance in galaxy clusters up to z=1.4

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    We present the combined analysis of the metal content of 83 objects in the redshift range 0.09-1.39, and spatially-resolved in the 3 bins (0-0.15, 0.15-0.4, >0.4) R500, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008) and Baldi et al. (2012). We use the pseudo-entropy ratio to separate the Cool-Core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the Non-Cool-Core systems. The average, redshift-independent, metal abundance measured in the 3 radial bins decrease moving outwards, with a mean metallicity in the core that is even 3 (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989) estimated at r>0.4 R500 in CC (NCC) objects. We find that the values of the emission-weighted metallicity are well-fitted by the relation Z(z)=Z0(1+z)γZ(z) = Z_0 (1+z)^{-\gamma} at given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05-0.15, is observed below 0.4 R500. The nominal best-fit value of γ\gamma is significantly different from zero in the inner cluster regions (γ=1.6±0.2\gamma = 1.6 \pm 0.2) and in CC clusters only. These results are confirmed also with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P>99.9 per cent). No redshift-evolution is observed when regions above the core (r > 0.15 R500) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form Z(r,z)=Z0(1+(r/0.15R500)2)β(1+z)γZ(r,z)=Z_0 (1+(r/0.15 R500)^2)^{-\beta} (1+z)^{-\gamma}, with (Z0,β,γ)=(0.83±0.13,0.55±0.07,1.7±0.6)(Z_0, \beta, \gamma) = (0.83 \pm 0.13, 0.55 \pm 0.07, 1.7 \pm 0.6) in CC clusters and (0.39±0.04,0.37±0.15,0.5±0.5)(0.39 \pm 0.04, 0.37 \pm 0.15, 0.5 \pm 0.5) for NCC systems. Our results represent the most extensive study of the spatially-resolved metal distribution in the cluster plasma as function of redshift.Comment: 5 pages. Research Note accepted for publication in A&

    A Chandra archival study of the temperature and metal abundance profiles in hot Galaxy Clusters at 0.1 < z < 0.3

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    We present the analysis of the temperature and metallicity profiles of 12 galaxy clusters in the redshift range 0.1--0.3 selected from the Chandra archive with at least ~20,000 net ACIS counts and kT>6 keV. We divide the sample between 7 Cooling-Core (CC) and 5 Non-Cooling-Core (NCC) clusters according to their central cooling time. We find that single power-laws can describe properly both the temperature and metallicity profiles at radii larger than 0.1 r_180 in both CC and NCC systems, showing the NCC objects steeper profiles outwards. A significant deviation is only present in the inner 0.1 r_180. We perform a comparison of our sample with the De Grandi & Molendi BeppoSAX sample of local CC and NCC clusters, finding a complete agreement in the CC cluster profile and a marginally higher value (at ~1sigma) in the inner regions of the NCC clusters. The slope of the power-law describing kT(r) within 0.1 r_180 correlates strongly with the ratio between the cooling time and the age of the Universe at the cluster redshift, being the slope >0 and tau_c/tau_age<=0.6 in CC systems.Comment: 12 pages, 6 figures, Accepted for publication by the Astrophysical Journa

    Fresh-cut salad and shelf life date extension: a segmentation of Italian consumers

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    Shelf-life estimation has become increasingly important due to the growing consumer interest in fresh and safe food products and the European policy indications to consider it as a key issue for the sustainable management of food waste within the supply chains. To date, no legislation on the shelf life date of the most of food products exists. Several studies demonstrate that logistic management and the technology available in the fresh-cut sector would allow to extend the shelf life date of products without compromising their intrinsic quality attributes and to achieve a more sustainable production by a strong reduction of unsold stock. The aim of the study was to segment consumers on the basis of their attitude towards the extension of the shelf life date in the fresh-cut salad sector. On the basis of the clusters found, the paper discusses if the information concerning such technology is a useful tool to inform consumers on product characteristics or if it entails a risk of information overload

    Rotation in galaxy clusters from MUSIC simulations with the kinetic Sunyaev-Zel'dovich effect

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    We propose in this work its application for the detection of possible coherent rotational motions in the hot intra-cluster medium. We select a sample of massive, relaxed and rotating galaxy clusters from Marenostrum-mUltidark SImulations of galaxy Clusters (MUSIC), and we produce mock maps of the temperature distortion produced by the kinetic Sunyaev-Zel'dovich effect by exploring six different lines of sight, in the best observational condition. These maps are compared with the expected signal computed from a suitable theoretical model in two cases: (i) focusing only on the contribution from the rotation, and (ii) accounting also for the cluster bulk motion. We find that the parameters of the model assumed for the radial profile of the rotational velocity, averaged over the considered lines of sight, are in agreement within two standard deviations at most with independent estimates from the simulation data, without being significantly affected by the presence of the cluster bulk term. The amplitude of the rotational signal is, on average, of the order of 23 per cent of the total signal accounting also for the cluster bulk motion, and its values are consistent with the literature. The projected bulk velocity of the cluster is also recovered at the different lines of sight, with values in agreement with the simulation dataASB acknowledges funding from Sapienza Università di Roma - Progetti per Avvio alla Ricerca Anno 2017, prot. AR11715C82402BC

    Containment Logics: Algebraic Completeness and Axiomatization

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    The paper studies the containment companion (or, right variable inclusion companion) of a logic ⊢. This consists of the consequence relation ⊢ r which satisfies all the inferences of ⊢ , where the variables of the conclusion are contained into those of the set of premises, in case this is not inconsistent. In accordance with the work started in [10], we show that a different generalization of the Płonka sum construction, adapted from algebras to logical matrices, allows to provide a matrix-based semantics for containment logics. In particular, we provide an appropriate completeness theorem for a wide family of containment logics, and we show how to produce a complete Hilbert style axiomatization

    Causes of hospitalization among extra-European Union children in a large hospital of Northern Italy, in a five-year observation period

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    The hospitalizations of 1,239 patients aged 14 years or less and immigrated from extra-European Union countries in Italy were assessed in the 6-year period, from 1999 to 2004. The main demographic and clinical features were analyzed according to several variables, also distiguishing patients aged less than one year, from those aged 1-14 years. The introduction of a deed of indemnity law in 2001 profoundly changed the pattern of admissions and health care needs and exploitation during subsequent years, leading to a massive regularization of clandestine immigrants

    The innovation potential of Islamic crowdfunding platforms in contributing to sustainable development

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    Purpose: This paper aims at explaining variances in the contribution of Islamic crowdfunding platforms (ICFPs) to sustainable development (SD), by adopting an institutional logic perspective (ILP). ICFPs represent a dual institutional overlap between two logics (the Western-mainstream and the Islamic logic) which have an impact on corporate social responsibility (CSR) interpretations, practices, and decisions and whose conflicts are mitigated by choosing different resolution strategies. The authors aim at showing that this choice affects SD differently. Design/methodology/approach: The authors develop a conceptual typology through the following steps: (1) choice of variables and identification of corresponding variable domains, through literature review. Variables chosen are the elemental CSR dimensions related to various social and environmental corporate responsibilities to whom diverse meaning and emphasis are given under the Western-mainstream and Islamic logics. (2) Identification of three distinct ideal types of ICFPs, building on different resolution strategies to mitigate conflicts between logics; (3) development, for each ideal type, of a set of implications related to SD; (4)&nbsp;implementation of a first test aiming at assigning real cases to each ideal type. Findings: The authors identify Western-mimicking (platforms adopting as resolution strategy decoupling or compartmentalizing strategies), Islamic-driven (platforms focusing on one prevailing logic) and Syncretism-inspired (platforms adopting hybridizing practices) ideal-types. Originality/value: It is the first paper suggesting ILP to explain variances in crowdfunding platforms' role in addressing SD. It focuses on a specific type of CF platforms till now neglected
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