1,116 research outputs found

### Thermodynamic properties and bulk viscosity near phase transition in the Z(2) and O(4) models

We investigate the thermodynamic properties including equation of state, the
trace anomaly, the sound velocity and the specific heat, as well as transport
properties like bulk viscosity in the Z(2) and O(4) models in the Hartree
approximation of Cornwall-Jackiw-Tomboulis (CJT) formalism. We study these
properties in different cases, e.g. first order phase transition, second order
phase transition, crossover and the case without phase transition, and discuss
the correlation between the bulk viscosity and the thermodynamic properties of
the system. We find that the bulk viscosity over entropy density ratio exhibits
an upward cusp at the second order phase transition, and a sharp peak at the
1st order phase transition. However, this peak becomes smooth or disappears in
the case of crossover. This indicates that at RHIC, where there is no real
phase transition and the system experiences a crossover, the bulk viscosity
over entropy density might be small, and it will not affect too much on
hadronization. We also suggest that the bulk viscosity over entropy density
ratio is a better quantity than the shear viscosity over entropy density ratio
to locate the critical endpoint.Comment: 19 pages, 30 figures, 1 tabl

### On Particle Production in Lead-Gold Collision and Azimuthal Anisotropy at Top SPS Energy

In a multisource thermal model, we analyze the dependence of elliptic flow v2 on the transverse momentum PT. The model results are compared with the data of π-, KS0, p, and Λ measured in Pb + Au collisions at top SPS energy, 17.3 GeV. It is found that the azimuthal anisotropy in the evolution process of high-energy collisions is correlated highly to the number of participant nucleons

### Higher-order effects on the incompressibility of isospin asymmetric nuclear matter

Analytical expressions for the saturation density as well as the binding
energy and incompressibility at the saturation density of asymmetric nuclear
matter are given exactly up to 4th-order in the isospin asymmetry delta =(rho_n
- rho_p)/rho using 11 characteristic parameters defined at the normal nuclear
density rho_0. Using an isospin- and momentum-dependent modified Gogny (MDI)
interaction and the SHF approach with 63 popular Skyrme interactions, we have
systematically studied the isospin dependence of the saturation properties of
asymmetric nuclear matter, particularly the incompressibility $K_{sat}(\delta
)=K_{0}+K_{sat,2}\delta ^{2}+K_{sat,4}\delta ^{4}+O(\delta ^{6})$ at the
saturation density. Our results show that the magnitude of the high-order
$K_{sat,4}$ parameter is generally small compared to that of the K_{\sat,2}
parameter. The latter essentially characterizes the isospin dependence of the
incompressibility at the saturation density and can be expressed as
$K_{sat,2}=K_{sym}-6L-\frac{J_{0}}{K_{0}}L$, Furthermore, we have constructed a
phenomenological modified Skyrme-like (MSL) model which can reasonably describe
the general properties of symmetric nuclear matter and the symmetry energy
predicted by both the MDI model and the SHF approach. The results indicate that
the high-order $J_{0}$ contribution to $K_{sat,2}$ generally cannot be
neglected. In addition, it is found that there exists a nicely linear
correlation between $K_{sym}$ and $L$ as well as between $J_{0}/K_{0}$ and
$K_{0}$. These correlations together with the empirical constraints on $K_{0}$,
$L$, $E_{sym}(\rho_{0})$ and the nucleon effective mass lead to an estimate of
$K_{sat,2}=-370\pm 120$ MeV.Comment: 61 pages, 12 figures, 6 Tables. Title changed a little and results of
several Skyrme interactions updated. Accepted version to appear in PR

### Aspect ratio dependence of heat transport by turbulent Rayleigh-B\'{e}nard convection in rectangular cells

We report high-precision measurements of the Nusselt number $Nu$ as a
function of the Rayleigh number $Ra$ in water-filled rectangular
Rayleigh-B\'{e}nard convection cells. The horizontal length $L$ and width $W$
of the cells are 50.0 cm and 15.0 cm, respectively, and the heights $H=49.9$,
25.0, 12.5, 6.9, 3.5, and 2.4 cm, corresponding to the aspect ratios
$(\Gamma_x\equiv L/H,\Gamma_y\equiv W/H)=(1,0.3)$, $(2,0.6)$, $(4,1.2)$,
$(7.3,2.2)$, $(14.3,4.3)$, and $(20.8,6.3)$. The measurements were carried out
over the Rayleigh number range $6\times10^5\lesssim Ra\lesssim10^{11}$ and the
Prandtl number range $5.2\lesssim Pr\lesssim7$. Our results show that for
rectangular geometry turbulent heat transport is independent of the cells'
aspect ratios and hence is insensitive to the nature and structures of the
large-scale mean flows of the system. This is slightly different from the
observations in cylindrical cells where $Nu$ is found to be in general a
decreasing function of $\Gamma$, at least for $\Gamma=1$ and larger. Such a
difference is probably a manifestation of the finite plate conductivity effect.
Corrections for the influence of the finite conductivity of the top and bottom
plates are made to obtain the estimates of $Nu_{\infty}$ for plates with
perfect conductivity. The local scaling exponents $\beta_l$ of $Nu_{\infty}\sim
Ra^{\beta_l}$ are calculated and found to increase from 0.243 at
$Ra\simeq9\times10^5$ to 0.327 at $Ra\simeq4\times10^{10}$.Comment: 15 pages, 7 figures, Accepted by Journal of Fluid Mechanic

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