411 research outputs found

    Veneziano like amplitude as a test for AdS/QCD models

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    The high energy asymptotics of QCD correlation functions is often used as a test for bottom-up holographic models. Since QCD is not strongly coupled in the ultraviolet domain, such a test may look questionable. We propose that the sum over resonance poles emerging in correlators of a bottom-up model should reproduce the structure of a Veneziano like amplitude at zero momentum transfer assuming equivalence of spin and radial states in the latter. This requires a five-dimensional background that suppresses the ultraviolet part in the effective action of a model. We give examples of emerging low-energy holographic models.Comment: 9 pages, accepted by the European Physical Journal C. arXiv admin note: substantial text overlap with arXiv:1102.274

    Weinberg like sum rules revisited

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    The generalized Weinberg sum rules containing the difference of isovector vector and axial-vector spectral functions saturated by both finite and infinite number of narrow resonances are considered. We summarize the status of these sum rules and analyze their overall agreement with phenomenological Lagrangians, low-energy relations, parity doubling, hadron string models, and experimental data.Comment: 31 pages, noticed misprints are corrected, references are added, and other minor corrections are mad

    About the possibility of five-dimensional effective theories for low-energy QCD

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    The AdS/QCD models suggest an interesting idea that the effective theory of low-energy QCD may be formulated as a 5-dimensional field theory in the weak coupling regime in which the fifth coordinate plays a role of inverse energy scale. Taking the point of view that this is just an efficient parametrization of the non-perturbative dynamics of strong interactions, we discuss on a qualitative level an alternative possibility for a simpler 5-dimensional parametrization of main phenomena in the low-energy QCD. We propose to interpret the effect of chiral symmetry breaking as an effective appearance of compactified extra dimension with the radius of the order of inverse scale of chiral symmetry breaking. Following some heuristic arguments two dual scenarios for the emergence of the excited light mesons are introduced: In the first scenario, the meson resonances are interpreted as the effects of Kaluza-Klein excitations of quarks inside mesons, in the second one, as the formation of gluon strings wound around the compactified dimension an appropriate number of times. Matching of these scenarios permits to express the slope of radial Regge trajectories through the order parameters of the chiral symmetry breaking, with the compactification radius being excluded. This example shows qualitatively that the extra dimension may play an auxiliary role providing a short way for deriving new relations.Comment: 11 pages, accepted by Eur. Phys. J.

    Extraction of the carbon ion beam from the U-70 accelerator into beamline 4a using a bent single crystal

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    A beam of six-charged carbon ions with an energy of 24.8 GeV/nucleon is extracted from the U-70 synchrotron by means of a silicon crystal bent through 85 mrad. A total of 200000 particles are observed in beamline 4a upon forcing 109 circulating ions to the crysta

    The measurement results of carbon ion beam structure extracted by bent crystal from U-70 accelerator

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    The carbon ion +6C beam with energy 25 GeV/nucleon was extracted by bent crystal from the U-70 ring. The bent angle of silicon crystal was 85 mrad. About 2*105 particles for 109 circulated ions in the ring were observed in beam line 4a after bent crystal. Geometrical parameters, time structure and ion beam structure were measure

    Is weak temperature dependence of electron dephasing possible?

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    The first-principle theory of electron dephasing by disorder-induced two state fluctuators is developed. There exist two mechanisms of dephasing. First, dephasing occurs due to direct transitions between the defect levels caused by inelastic electron-defect scattering. The second mechanism is due to violation of the time reversal symmetry caused by time-dependent fluctuations of the scattering potential. These fluctuations originate from an interaction between the dynamic defects and conduction electrons forming a thermal bath. The first contribution to the dephasing rate saturates as temperature decreases. The second contribution does not saturate, although its temperature dependence is rather weak, T1/3\propto T^{1/3}. The quantitative estimates based on the experimental data show that these mechanisms considered can explain the weak temperature dependence of the dephasing rate in some temperature interval. However, below some temperature dependent on the model of dynamic defects the dephasing rate tends rapidly to zero. The relation to earlier studies of the dephasing caused by the dynamical defects is discussed.Comment: 14 pages, 6 figures, submitted to PR

    Importance of extracorporeal membrane oxygenation (ECMO) in therapy for legionella pneumonia in patient with hairy-cell leucosis

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    Clinical observation of the patient with legionella pneumonia which developed in the setting of hairy-cell leukosis, required use of extracorporeal membrane oxygenation for controlling life-threatening hypoxia is presented. Active diagnostic approach for identification of the etiologic agent (Legionella pneumophila, Acinetobacter baumannii) that caused pneumonia, allowed to choose an optimum set of antibacterial agents and medicines for specific therapy of hemoblastosis (BRAFV600E mutation and use of Zelboraf). After correction of respiratory insufficiency and discontinue the patient from ECMO, we could reach hematologic remission and transfer the patient to the Institute of Hematology for further treatment
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