16,838 research outputs found

    Unifying the Fixed Order Evolution of Fragmentation Functions with the Modified Leading Logarithm Approximation

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    An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches

    Anderson transitions in three-dimensional disordered systems with randomly varying magnetic flux

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    The Anderson transition in three dimensions in a randomly varying magnetic flux is investigated in detail by means of the transfer matrix method with high accuracy. Both, systems with and without an additional random scalar potential are considered. We find a critical exponent of ν=1.45±0.09\nu=1.45\pm0.09 with random scalar potential. Without it, ν\nu is smaller but increases with the system size and extrapolates within the error bars to a value close to the above. The present results support the conventional classification of universality classes due to symmetry.Comment: 4 pages, 2 figures, to appear in Phys. Rev.

    Observables in the Decays of B to Two Vector Mesons

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    In general there are nine observables in the decay of a B meson to two vector mesons defined in terms of polarization correlations of these mesons. Only six of these can be detected via the subsequent decay angular distributions because of parity conservation in those decays. The remaining three require the measurement of the spin polarization of one of the decay products.Comment: 12 pages, no figur

    Detection of the gravitomagnetic clock effect

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    The essence of the gravitomagnetic clock effect is properly defined showing that its origin is in the topology of world lines with closed space projections. It is shown that, in weak field approximation and for a spherically symmetric central body, the loss of synchrony between two clocks counter-rotating along a circular geodesic is proportional to the angular momentum of the source of the gravitational field. Numerical estimates are presented for objects within the solar system. The less unfavorable situation is found around Jupiter.Comment: 14 pages; Latex. To be published on Classical and Quantum Gravit

    Long-term Observations of Three Nulling Pulsars

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    We present an analysis of approximately 200 hours of observations of the pulsars J1634−-5107, J1717−-4054 and J1853++0505, taken over the course of 14.7 yr. We show that all of these objects exhibit long term nulls and radio-emitting phases (i.e. minutes to many hours), as well as considerable nulling fractions (NFs) in the range ∼67 %−90 %\sim67\,\% - 90\,\%. PSR J1717−-4054 is also found to exhibit short timescale nulls (1−40 P1 - 40~P) and burst phases (≲200 P\lesssim 200~P) during its radio-emitting phases. This behaviour acts to modulate the NF, and therefore the detection rate of the source, over timescales of minutes. Furthermore, PSR J1853++0505 is shown to exhibit a weak emission state, in addition to its strong and null states, after sufficient pulse integration. This further indicates that nulls may often only represent transitions to weaker emission states which are below the sensitivity thresholds of particular observing systems. In addition, we detected a peak-to-peak variation of 33±1 %33\pm1\,\% in the spin-down rate of PSR J1717−-4054, over timescales of hundreds of days. However, no long-term correlation with emission variation was found.Comment: 10 pages, 8 figures, accepted for publication in MNRA

    Apollo-11 lunar sample information catalogue

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    The Apollo 11 mission is reviewed with emphasis on the collection of lunar samples, their geologic setting, early processing, and preliminary examination. The experience gained during five subsequent missions was applied to obtain physical-chemical data for each sample using photographic and binocular microscope techniques. Topics discussed include: binocular examination procedure; breccia clast dexrriptuons, thin section examinations procedure typical breccia in thin section, typical basalt in thin section, sample histories, and chemical and age data. An index to photographs is included

    Hysteresis in the de Haas-van Alphen Effect

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    A hysteresis loop is observed for the first time in the de Haas-van Alphen (dHvA) effect of beryllium at low temperatures and quantizing magnetic field applied parallel to the hexagonal axis of the single crystal. The irreversible behavior of the magnetization occurs at the paramagnetic part of the dHvA period in conditions of Condon domain formation arising by strong enough dHvA amplitude. The resulting extremely nonlinear response to a very small modulation field offers the possibility to find in a simple way the Condon domain phase diagram. From a harmonic analysis, the shape and size of the hysteresis loop is constructed.Comment: 4 pages, 5 figures, submitted to PR

    Neutron Stars as Type-I Superconductors

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    In a recent paper by Link, it was pointed out that the standard picture of the neutron star core composed of a mixture of a neutron superfluid and a proton type-II superconductor is inconsistent with observations of a long period precession in isolated pulsars. In the following we will show that an appropriate treatment of the interacting two-component superfluid (made of neutron and proton Cooper pairs), when the structure of proton vortices is strongly modified, may dramatically change the standard picture, resulting in a type-I superconductor. In this case the magnetic field is expelled from the superconducting regions of the neutron star leading to the formation of the intermediate state when alternating domains of superconducting matter and normal matter coexist.Comment: 4 page
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