26,029 research outputs found

    GeMs/GSAOI observations of La Serena 94: an old and far open cluster inside the solar circle

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    Physical properties were derived for the candidate open cluster La Serena 94, recently unveiled by the VVV collaboration. Thanks to the exquisite angular resolution provided by GeMS/GSAOI, we could characterize this system in detail, for the first time, with deep photometry in JHKs_{s} - bands. Decontaminated JHKs_{s} diagrams reach about 5 mag below the cluster turnoff in H. The locus of red clump giants in the colour - colour diagram, together with an extinction law, was used to obtain an average extinction of AV=14.18±0.71A_V =14.18 \pm 0.71. The same stars were considered as standard - candles to derive the cluster distance, 8.5±1.08.5 \pm 1.0 kpc. Isochrones were matched to the cluster colour - magnitude diagrams to determine its age, logt(yr)=9.12±0.06\log{t(yr)}=9.12\pm 0.06, and metallicity, Z=0.02±0.01Z=0.02\pm0.01. A core radius of rc=0.51±0.04r_{c}=0.51\pm 0.04 pc was found by fitting King models to the radial density profile. By adding up the visible stellar mass to an extrapolated mass function, the cluster mass was estimated as M=(2.65±0.57)×103M=(2.65\pm0.57) \times 10^3 M_{\odot}, consistent with an integrated magnitude of MK=5.82±0.16M_{K}=-5.82\pm0.16 and a tidal radius of rt=17.2±2.1r_{t}=17.2\pm2.1 pc. The overall characteristics of La Serena 94 confirm that it is an old open cluster located in the Crux spiral arm towards the fourth Galactic quadrant and distant 7.30±0.497.30\pm 0.49 kpc from the Galactic centre. The cluster distorted structure, mass segregation and age indicate that it is a dynamically evolved stellar system.Comment: 16 pages, 24 figures, 2 Tables, accepted by MNRAS; corrected typo

    A dynamical point of view of Quantum Information: entropy and pressure

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    Quantum Information is a new area of research which has been growing rapidly since last decade. This topic is very close to potential applications to the so called Quantum Computer. In our point of view it makes sense to develop a more "dynamical point of view" of this theory. We want to consider the concepts of entropy and pressure for "stationary systems" acting on density matrices which generalize the usual ones in Ergodic Theory (in the sense of the Thermodynamic Formalism of R. Bowen, Y. Sinai and D. Ruelle). We consider the operator L\mathcal{L} acting on density matrices ρMN\rho\in \mathcal{M}_N over a finite NN-dimensional complex Hilbert space L(ρ):=i=1ktr(WiρWi)ViρVi,\mathcal{L}(\rho):=\sum_{i=1}^k tr(W_i\rho W_i^*)V_i\rho V_i^*, where WiW_i and ViV_i, i=1,2,...ki=1,2,...k are operators in this Hilbert space. L\mathcal{L} is not a linear operator. In some sense this operator is a version of an Iterated Function System (IFS). Namely, the Vi(.)Vi=:Fi(.)V_i\,(.)\,V_i^*=:F_i(.), i=1,2,...,ki=1,2,...,k, play the role of the inverse branches (acting on the configuration space of density matrices ρ\rho) and the WiW_i play the role of the weights one can consider on the IFS. We suppose that for all ρ\rho we have that i=1ktr(WiρWi)=1\sum_{i=1}^k tr(W_i\rho W_i^*)=1. A family W:={Wi}i=1,...,kW:=\{W_i\}_{i=1,..., k} determines a Quantum Iterated Function System (QIFS) FW\mathcal{F}_{W}, $\mathcal{F}_W=\{\mathcal{M}_N,F_i,W_i\}_{i=1,..., k}.

    A dynamical point of view of Quantum Information: Wigner measures

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    We analyze a known version of the discrete Wigner function and some connections with Quantum Iterated Funcion Systems. This paper is a follow up of "A dynamical point of view of Quantum Information: entropy and pressure" by the same authors

    A Thermodynamic Formalism for density matrices in Quantum Information

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    We consider new concepts of entropy and pressure for stationary systems acting on density matrices which generalize the usual ones in Ergodic Theory. Part of our work is to justify why the definitions and results we describe here are natural generalizations of the classical concepts of Thermodynamic Formalism (in the sense of R. Bowen, Y. Sinai and D. Ruelle). It is well-known that the concept of density operator should replace the concept of measure for the cases in which we consider a quantum formalism. We consider the operator Λ\Lambda acting on the space of density matrices MN\mathcal{M}_N over a finite NN-dimensional complex Hilbert space Λ(ρ):=i=1ktr(WiρWi)ViρVitr(ViρVi), \Lambda(\rho):=\sum_{i=1}^k tr(W_i\rho W_i^*)\frac{V_i\rho V_i^*}{tr(V_i\rho V_i^*)}, where WiW_i and ViV_i, i=1,2,...,ki=1,2,..., k are linear operators in this Hilbert space. In some sense this operator is a version of an Iterated Function System (IFS). Namely, the Vi(.)Vi=:Fi(.)V_i\,(.)\,V_i^*=:F_i(.), i=1,2,...,ki=1,2,...,k, play the role of the inverse branches (i.e., the dynamics on the configuration space of density matrices) and the WiW_i play the role of the weights one can consider on the IFS. In this way a family W:={Wi}i=1,...,kW:=\{W_i\}_{i=1,..., k} determines a Quantum Iterated Function System (QIFS). We also present some estimates related to the Holevo bound

    National industry cluster templates and the structure of industry output dynamics: a stochastic geometry approach

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    Cluster analysis has been widely used in an Input-Output framework, with the main objective of uncover the structure of production, in order to better identify which sectors are strongly connected with each other and choose the key sectors of a national or regional economy. There are many empirical studies determining potential clusters from interindustry flows directly, or from their corresponding technical (demand) or market (supply) coefficients, most of them applying multivariate statistical techniques. In this paper, after identifying clusters this way, and since it may be expected that strongly (interindustry) connected sectors share a similar growth and development path, the structure of sectoral dynamics is uncovered, by means of a stochastic geometry technique based on the correlations of industry outputs in a given period of time. An application is made, using Portuguese input-output data, and the results do not clearly support this expectation.Clusters, Input-output analysis, Industry output dynamics

    Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics

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    Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites
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