3,926 research outputs found

    Nuclear phenomena derived from quark-gluon strings

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    We propose a QCD based many-body model for the nucleus where the strong coupling regime is controlled by a three body string force and the weak coupling regime is dominated by a pairing force. This model operates effectively with a quark-gluon Lagrangian containing a pairing force from instantons and a baryonic string term which contains a confining potential. The unified model for weak and strong coupling regimes, is, however, only consistent at the border of perturbative QCD. The baryonic string force is necessary, as a {stability and} compressibility analysis shows, for the occurrence of the phases of nuclear matter. The model exhibits a quark deconfinement transition and chiral restoration which are suggested by QCD and give qualitatively correct numerics. The effective model is shown to be isomorphic to the Nambu-Jona-Lasinio model and exhibits the correct chirality provided that the chiral fields are identified with the 2-particle strings, which are natural in a QCD frameworkComment: 17 pages, 4 figures, 2 table

    Representation of SU(infinity) Algebra for Matrix Models

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    We investigate how the matrix representation of SU(N) algebra approaches that of the Poisson algebra in the large N limit. In the adjoint representation, the (N^2-1) times (N^2-1) matrices of the SU(N) generators go to those of the Poisson algebra in the large N limit. However, it is not the case for the N times N matrices in the fundamental representation.Comment: 8 page

    Import/Export in Digital Rights Management

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    The inherently controlled nature of digital rights management systems does little to promote inter-operability of systems provided by different vendors. In this paper, we consider import and export functionality by which multimedia protected by one digital rights management regime can be made available to a multimedia device that supports a different digital rights management regime, without compromising the protection afforded to the content under the original regime. We first identify specific issues to be addressed by developers of digital rights management import/export regimes and outline a variety of methods by which these regimes may be implemented. We then apply our observations to the specific example of import and export of content between the digital rights management regimes defined by the Motion Picture Exports Group and the Open Mobile Alliance

    Spatial and temporal filtering of a 10-W Nd:YAG laser with a Fabry-Perot ring-cavity premode cleaner

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    We report on the use of a fixed-spacer Fabry–Perot ring cavity to filter spatially and temporally a 10-W laser-diode-pumped Nd:YAG master-oscillator power amplifier. The spatial filtering leads to a 7.6-W TEMinfinity beam with 0.1% higher-order transverse mode content. The temporal filtering reduces the relative power fluctuations at 10 MHz to 2.8 x 10^-/sqrtHz, which is 1 dB above the shot-noise limit for 50 mA of detected photocurrent

    Perturbation Theory for a Repulsive Hubbard Model in Quasi-One-Dimensional Superconductors

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    We investigate pairing symmetry and a transition temperature in a quasi-one-dimensional repulsive Hubbard model. We solve the Eliashberg equation using the third-order perturbation expansion with respect to the on-site repulsion UU. We find that when the electron number density is shifted from the half-filled, a transition into unconventional superconductivity is expected. When one dimensionality is weak, a spin-singlet state is favorable. By contrast, when one dimensionality is strong and electron number density is far from the half-filled, a spin-triplet state is stabilized. Finally, we discuss the possibility of unconventional superconductivity caused by the on-site Coulomb repulsion in β\beta-Na0.33_{0.33}V2_2O5_5.Comment: 4 pages, 7 figure

    Sublinear Estimation of Weighted Matchings in Dynamic Data Streams

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    This paper presents an algorithm for estimating the weight of a maximum weighted matching by augmenting any estimation routine for the size of an unweighted matching. The algorithm is implementable in any streaming model including dynamic graph streams. We also give the first constant estimation for the maximum matching size in a dynamic graph stream for planar graphs (or any graph with bounded arboricity) using O~(n4/5)\tilde{O}(n^{4/5}) space which also extends to weighted matching. Using previous results by Kapralov, Khanna, and Sudan (2014) we obtain a polylog(n)\mathrm{polylog}(n) approximation for general graphs using polylog(n)\mathrm{polylog}(n) space in random order streams, respectively. In addition, we give a space lower bound of Ω(n1ε)\Omega(n^{1-\varepsilon}) for any randomized algorithm estimating the size of a maximum matching up to a 1+O(ε)1+O(\varepsilon) factor for adversarial streams

    Scaling Properties of Antiferromagnetic Transition in Coupled Spin Ladder Systems Doped with Nonmagnetic Impurities

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    We study effects of interladder coupling on critical magnetic properties of spin ladder systems doped with small concentrations of nonmagnetic impurities, using the scaling theory together with quantum Monte Carlo (QMC) calculations. Scaling properties in a wide region in the parameter space of the impurity concentration x and the interladder coupling are governed by the quantum critical point (QCP) of the undoped system for the transition between antiferromagnetically ordered and spin-gapped phases. This multi-dimensional and strong-coupling region has characteristic power-law dependences on x for magnetic properties such as the N\'eel temperature. The relevance of this criticality for understanding experimental results of ladder compounds is stressed.Comment: 4 pages LaTeX including 3 PS figure

    A critical-density closed Universe in Brans-Dicke theory

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    In a Brans-Dicke (BD) cosmological model, the energy density associated with some scalar field decreases as \displaystyle a^{{-2}(\frac{\omega_{o}+ {\frac12}%}{\omega_{o}+1})} with the scale factor a(t)a(t) of the Universe, giving a matter with an Equation of state p=1/3(2+ωo1+ωo)ρ\displaystyle p=-{1/3}(\frac{2+\omega_{o}}{1+\omega_{o}}) \rho . In this model, the Universe could be closed but still have a nonrelativistic-matter density corresponding to its critical value, Ωo=1\Omega_{o}=1. Different cosmological expressions, such as, luminosity distance, angular diameter, number count and ratio of the redshift tickness-angular size, are determined in terms of the redshift for this model.Comment: To appear in MNRAS, 7 pages, 5 eps figure
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