5,329 research outputs found

    Mass formulae and strange quark matter

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    We have derived the popularly used parametrization formulae for quark masses at low densities and modified them at high densities within the mass-density-dependent model. The results are applied to investigate the lowest density for the possible existence of strange quark matter at zero temperature.Comment: 9 pages, LATeX with ELSART style, one table, no figures. Improvement on the derivation of qark mass formula

    On the momentum-dependence of KK^{-}-nuclear potentials

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    The momentum dependent KK^{-}-nucleus optical potentials are obtained based on the relativistic mean-field theory. By considering the quarks coordinates of KK^- meson, we introduced a momentum-dependent "form factor" to modify the coupling vertexes. The parameters in the form factors are determined by fitting the experimental KK^{-}-nucleus scattering data. It is found that the real part of the optical potentials decrease with increasing KK^- momenta, however the imaginary potentials increase at first with increasing momenta up to Pk=450550P_k=450\sim 550 MeV and then decrease. By comparing the calculated KK^- mean free paths with those from KnK^-n/KpK^-p scattering data, we suggested that the real potential depth is V080V_0\sim 80 MeV, and the imaginary potential parameter is W065W_0\sim 65 MeV.Comment: 9 pages, 4 figure

    Chiral Condensates in Quark and nuclear Matter

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    We present a novel treatment for calculating the in-medium quark condensates. The advantage of this approach is that one does not need to make further assumptions on the derivatives of model parameters with respect to the quark current mass. The normally accepted model-independent result in nuclear matter is naturally reproduced. The change of the quark condensate induced by interactions depends on the incompressibility of nuclear matter. When it is greater than 260 MeV, the density at which the condensate vanishes is higher than that from the linear extrapolation. For the chiral condensate in quark matter, a similar model-independent linear behavior is found at lower densities, which means that the decreasing speed of the condensate in quark matter is merely half of that in nuclear matter if the pion-nucleon sigma commutator is six times the average current mass of u and d quarks. The modification due to QCD-like interactions is found to slow the decreasing speed of the condensate, compared with the linear extrapolation.Comment: 12 pages, 7 figures, revtex4 styl

    In-medium Properties of Θ+\Theta^{+} as a Kπ\piN structure in Relativistic Mean Field Theory

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    The properties of nuclear matter are discussed with the relativistic mean-field theory (RMF).Then, we use two models in studying the in-medium properties of Θ+\Theta^+: one is the point-like Θ\Theta^* in the usual RMF and the other is a Kπ\piN structure for the pentaquark. It is found that the in-medium properties of Θ+\Theta^+ are dramatically modified by its internal structure. The effective mass of Θ+\Theta^+ in medium is, at normal nuclear density, about 1030 MeV in the point-like model, while it is about 1120 MeV in the model of Kπ\piN pentaquark. The nuclear potential depth of Θ+\Theta^+ in the Kπ\piN model is approximately -37.5 MeV, much shallower than -90 MeV in the usual point-like RMF model.Comment: 8 pages, 5 figure

    Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets

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    Thermodynamic formulas for investigating systems with density and/or temperature dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low mass strangelets near beta equilibrium are multi-quark states with an anti-strange quark, such as the pentaquark (u^2d^2\bar{s}) for baryon nmber 1 and the octaquark (u^4d^3\bar{s}) for dibaryon etc.Comment: 14 pages, 12 figures, Revtex4 styl

    The ΣΣ\Sigma\Sigma interactions in finite-density QCD sum rules

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    The properties of Σ\Sigma-hyperons in pure Σ\Sigma matter are studied with the finite-density quantum chromo-dynamics sum rule (QCDSR) approach. The ΣΣ\Sigma\Sigma nuclear potential UΣU_\Sigma is most likely strongly attractive, it could be about -50 MeV or even more attractive at normal nuclear density. If this prediction is the case, the interactions between Σ\Sigma-hyperons should play crucial roles in the strange nuclear matter, when there are multi-Σ\Sigma hyperons. The bound state of double-Σ\Sigma maybe exist.Comment: Latex, 9 pages with 10 figure

    Standing wave oscillations in binary mixture convection: from onset via symmetry breaking to period doubling into chaos

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    Oscillatory solution branches of the hydrodynamic field equations describing convection in the form of a standing wave (SW) in binary fluid mixtures heated from below are determined completely for several negative Soret coefficients. Galerkin as well as finite-difference simulations were used. They were augmented by simple control methods to obtain also unstable SW states. For sufficiently negative Soret coefficients unstable SWs bifurcate subcritically out of the quiescent conductive state. They become stable via a saddle-node bifurcation when lateral phase pinning is exerted. Eventually their invariance under time-shift by half a period combined with reflexion at midheight of the fluid layer gets broken. Thereafter they terminate by undergoing a period-doubling cascade into chaos
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