5,329 research outputs found

### 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

### On the momentum-dependence of $K^{-}$-nuclear potentials

The momentum dependent $K^{-}$-nucleus optical potentials are obtained based
on the relativistic mean-field theory. By considering the quarks coordinates of
$K^-$ 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 $K^{-}$-nucleus scattering data. It is found that the real
part of the optical potentials decrease with increasing $K^-$ momenta, however
the imaginary potentials increase at first with increasing momenta up to
$P_k=450\sim 550$ MeV and then decrease. By comparing the calculated $K^-$ mean
free paths with those from $K^-n$/$K^-p$ scattering data, we suggested that the
real potential depth is $V_0\sim 80$ MeV, and the imaginary potential parameter
is $W_0\sim 65$ MeV.Comment: 9 pages, 4 figure

### 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 $\Theta^{+}$ as a K$\pi$N 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

### 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

### The $\Sigma\Sigma$ interactions in finite-density QCD sum rules

The properties of $\Sigma$-hyperons in pure $\Sigma$ matter are studied with
the finite-density quantum chromo-dynamics sum rule (QCDSR) approach. The
$\Sigma\Sigma$ nuclear potential $U_\Sigma$ 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 $\Sigma$-hyperons should
play crucial roles in the strange nuclear matter, when there are multi-$\Sigma$
hyperons. The bound state of double-$\Sigma$ 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

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

- â€¦