425 research outputs found

    Pion-delta sigma-term

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    We use a configuration space chiral model in order to evaluate nucleon and delta sigma-terms. Analytic expressions are consistent with chiral counting rules and give rise to expected non-analytic terms in the chiral limit. We obtain the results σN=46\sigma_N=46 MeV and σΔ=32\sigma_{\Delta}=32 MeV, which are very close to values extracted from experiment and produced by other groups.Comment: 18 pages, 4 figure

    Collective Quantisation of a Gravitating Skyrmion

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    Collective quantisation of a B=1 gravitating skyrmion is described. The rotational and isorotational modes are quantised in the same manner as the skyrmion without gravity. It is shown in this paper how the static properties of nucleons such as masses, charge densities, magnetic moments are modified by the gravitational interaction.Comment: 10 pages, 9 figures, minor corrections, published versio

    Chiral symmetry breaking and vacuum polarization in a bag

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    We study the effects of a finite quark mass in the hedgehog configuration in the two phase chiral bag model. We discuss the chiral properties, such as the fractional baryon number and the chiral Casimir energy, by using the Debye expansion for the analytical calculation and the Strutinsky's smearing method for the numerical computation. It is shown that the fractional baryon number carried by massive quarks in the vacuum is canceled by that in the meson sector. A finite term of the chiral Casimir energy is obtained with subtraction of the logarithmic divergence term

    Topology in Physics - A Perspective

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    This article, written in honor of Fritz Rohrlich, briefly surveys the role of topology in physics.Comment: 16pp, 2 figures included (encapsulated postscript

    Topological Objects in Two-component Bose-Einstein Condensates

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    We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensate, the popular Gross-Pitaevskii theory and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-Einstein condensate, with the U(1) gauge symmetry, is remarkably similar to the Skyrme theory. Just like the Skyrme theory the theory admits the non-Abelian vortex, the helical vortex, and the vorticity knot. We construct the lightest knot solution in two-component Bose-Einstein condensate numerically, and discuss how the knot can be constructed in the spin-1/2 condensate of 87Rb^{87}{\rm Rb} atoms.Comment: 18 pages, 15 figures, Phys. Rev. A in pres

    The nucleus as a fluid of skyrmions: Energy levels and nucleon properties in the medium

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    A model of a fluid of skyrmions coupled to a scalar and to the \o meson mean fields is developed. The central and spin-orbit potentials of a skyrmion generated by the fields predict correct energy levels in selected closed shell nuclei. The effect of the meson fields on the properties of skyrmions in nuclei is investigated.Comment: Latex format, 6 figures, Journal of Physics G, to be publishe

    ppK- bound states from Skyrmions

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    The bound kaon approach to the strangeness in the Skyrme model is applied to investigating the possibility of deeply bound ppKppK^- states. We describe the ppKppK^- system as two-Skyrmion around which a kaon field fluctuates. Each Skyrmion is rotated in the space of SU(2) collective coordinate. The rotational motions are quantized to be projected onto the spin-singlet proton-proton state. We derive the equation of motion for the kaon in the background field of two Skyrmions at fixed positions. From the numerical solution of the equation of motion, it is found that the energy of KK^- can be considerably small, and that the distribution of KK^- shows molecular nature of the ppKppK^- system. For this deep binding, the Wess-Zumino-Witten term plays an important role. The total energy of the ppKppK^- system is estimated in the Born-Oppenheimer approximation. The binding energy of the ppKppK^- state is B.E.126B.E.\simeq 126 MeV. The mean square radius of the pppp subsystem is 1.6\sqrt{}\simeq 1.6 fm.Comment: Oct 2007, 15 pages, 8 figures; added references, corrected typo

    On the electromagnetic form factors of the proton from generalized Skyrme models

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    We compare the prediction of Skyrme-like effective Lagrangians with data for electromagnetic form factors of proton and consider the possibility of fixing the parameters of these higher-order Lagrangians. Our results indicate that one or two-parameter models can lead to better agreement with the data but more accurate determination of the effective Lagragian faces theoretical uncertainties.Comment: 8 pages, 2 figures, revte

    High-density Skyrmion matter and Neutron Stars

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    We examine neutron star properties based on a model of dense matter composed of B=1 skyrmions immersed in a mesonic mean field background. The model realizes spontaneous chiral symmetry breaking non-linearly and incorporates scale-breaking of QCD through a dilaton VEV that also affects the mean fields. Quartic self-interactions among the vector mesons are introduced on grounds of naturalness in the corresponding effective field theory. Within a plausible range of the quartic couplings, the model generates neutron star masses and radii that are consistent with a preponderance of observational constraints, including recent ones that point to the existence of relatively massive neutron stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron stars with such dimensions is confirmed, matter at supra-nuclear density is stiffer than extrapolations of most microscopic models suggest.Comment: 27 pages, 5 figures, AASTeX style; to be published in The Astrophysical Journa

    Spin textures in slowly rotating Bose-Einstein Condensates

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    Slowly rotating spin-1 Bose-Einstein condensates are studied through a variational approach based upon lowest Landau level calculus. The author finds that in a gas with ferromagnetic interactions, such as 87^{87}Rb, angular momentum is predominantly carried by clusters of two different types of skyrmion textures in the spin-vector order parameter. Conversely, in a gas with antiferromagnetic interactions, such as 23^{23}Na, angular momentum is carried by π\pi-disclinations in the nematic order parameter which arises from spin fluctuations. For experimentally relevant parameters, the cores of these π\pi-disclinations are ferromagnetic, and can be imaged with polarized light.Comment: 14 pages, 12 low resolution bitmapped figures, RevTeX4. High resolution figures available from author. Suplementary movies available from autho
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