Mass formulae and strange quark matter

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

Chiral Condensates in Quark and nuclear Matter

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

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 $\Theta^+$: one is the point-like $\Theta^*$ in the usual RMF and the other is a K$\pi$N structure for the pentaquark. It is found that the in-medium properties of $\Theta^+$ are dramatically modified by its internal structure. The effective mass of $\Theta^+$ 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 K$\pi$N pentaquark. The nuclear potential depth of $\Theta^+$ in the K$\pi$N model is approximately -37.5 MeV, much shallower than -90 MeV in the usual point-like RMF model.Comment: 8 pages, 5 figure

High Sensitivity Hot-wire based Wind Velocity Sensor using Co-doped Fiber and Fiber Bragg Grating for use in mining applications

In this paper, a mathematical model of the temperature distribution in a fiber-optic version of the familiar 'hot-wire' wind velocity sensor has been established and a practical sensor device realized and investigated for use in coal mining applications. The relationship between the dynamic measurement range, the sensitivity, the sensor probe surface heat transfer coefficient and the wind speed (in the region where the sensor probe is located) has been investigated. The veracity of the predicted performance of the fiber-optic hot-wire mathematical model has then been verified by experiment. The sensitivity of the sensor probe to wind velocity was measured across several wind velocity ranges to be ∼1500pm per unit m/s wind velocity (in the range of 0 - 0.5 m/s), ∼330pm per unit m/s in the range 0.5 - 2 m/s and ∼50pm per unit m/s in the range of 2.0 - 4.5 m/s

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

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

Possible superconductivity above 25 K in single crystalline Co-doped BaFe2_{2}As2_{2}

We present superconducting properties of single crystalline Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ by measuring magnetization, resistivity, upper critical field, Hall coefficient, and magneto-optical images. The magnetization measurements reveal fish-tail hysteresis loop at high temperatures and relatively high critical current density above $J_{c}=10^{5}$ A/cm$^{2}$ at low temperatures. Upper critical field determined by resistive transition is anisotropic with anisotropic parameter $\sim$ 3.5. Hall effect measurements indicate that Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ is a multiband system and the mobility of electron is dominant. The magneto-optical imaging reveals prominent Bean-like penetration of vortices although there is a slight inhomogeneity in a sample. Moreover, we find a distinct superconductivity above 25 K, which leads us to speculate that higher transition temperature can be realized by fine tuning Co-doping level.Comment: 4 pages, 5 figure