关于QGP中夸克屏蔽位势来自动力论方程的研究

从ＱＧＰ的动力论方程出发，计及运动检验夸克的色电场扰动，采用微扰方法，并在高温极限下得到ＱＧＰ中夸克的分布函数和色电势．给出了考虑运动效应在内的德拜长度λＤ（或屏蔽质量ωＤ）与温度Ｔ的关系，在静态极限下它们与ＱＣＤ理论相符．     

Thermo-field dynamics and quark–hadron phase transition in QCD

Based on the topological structure of gauge theory, an effective dual version of QCD has been reviewed and analyzed for the phase structure and color confining properties of QCD by invoking the dynamical magnetic symmetry breaking. The multi-flux-tube configuration of condensed QCD vacuum has been explored and associated glueball masses and inter-quark potential have been derived. Thermal response of QCD vacuum has been analyzed using path-integral formalism alongwith the mean-field approach and associated thermodynamical potential is used to derive thermal form of glueball masses, monopole condensate, inter-quark potential and monopole density which then lead to an estimate of the critical temperature of QCD phase transition. During its thermal evolution, a smooth transition of hadronic system via a weakly bound QGP phase to the fully deconfined phase is established and the thermal evolution profiles of various parameters are shown to indicate a second-order deconfinement phase transition and the restoration of magnetic symmetry. Monopole density calculations have been shown to lead to gradual evaporation of magnetic condensate into thermal monopoles during QCD phase transition.     

Loss in a rectangular optical waveguide induced by the crossover of a second waveguide

We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design.     

液体横向射流在气膜作用下的破碎过程

为了研究液体横向射流在气膜作用下的破碎过程,采用背景光成像技术及VOF TO DPM方法进行了实验研究和仿真研究,模拟介质为水和空气.研究结果表明,液体射流在气膜作用下主要存在两种破碎过程:柱状破碎和表面破碎.Rayleigh-Taylor(R-T)不稳定性产生的表面波是液体射流发生柱状破碎的主要原因,气流穿透表面波的波谷导致射流柱破碎,破碎后的液丝沿流向逐渐发展呈带状分布.Kelvin-Helmholtz(K-H)不稳定性产生的表面波是液体射流发生表面破碎的主要原因,液丝和液滴从射流表面剥离.局部动量比对液体横向射流的破碎过程具有重要影响,当局部动量比较低时,液体射流的破碎由K-H不稳定性主导;随着局部动量比的增大液体射流的破碎逐渐由R-T不稳定性主导.液体射流的破碎长度及穿透深度均随局部动量比的增大而增大.     

Density correlations of hadron gas and the origin of early multiplicity scaling

We will define a sequence of functions called density correlations which measure statistical correlations between momentum space densities of particles in the ensemble of inelastic final states produced by scattering a pair of hadrons. Then we will show that early multiplicity scaling of the distribution of charged particles produced by pp collisions can primarly be explained by the assumption that fluctuations of the density of charged particles are quite random and therefore higher correlation functions are small in an appropriate sense, combined with the assumption that the first three density correlations fulfill an approximate form of Feyman scaling at small values of x. These assumptions will aslo be used to derive an expression for the scaling function Ψ(η) which is completely determined by <N²>_S/<N>_S² and <N³>_S/<N>_S³, and recursion relation to calculate <N^m>_S/<N>_S^m, m ? 4, from <N²>_S/<N>_S² and <N³>_S/<N>_S³. The prediction for Ψ(η) accurately reproduces data in the interval 0.2 ? η ? 3.1, 50 GeV/c ? p_L ? 303 GeV/c, and the predictions for <N_S>^m/<N>_S^m, 4 ? m ? 10, agree with observed values in the interval 50 GeV/c ? p_L ? 303 GeV/c.     

Cross-correlations between agricultural commodity futures markets in the US and China

This paper examines the cross-correlation properties of agricultural futures markets between the US and China using a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). The results show that the cross-correlations between the two geographically distant markets for four pairs of important agricultural commodities futures are significantly multifractal. By introducing the concept of a “crossover”, we find that the multifractality of cross-correlations between the two markets is not long lasting. The cross-correlations in the short term are more strongly multifractal, but they are weakly so in the long term. Moreover, cross-correlations of small fluctuations are persistent and those of large fluctuations are anti-persistent in the short term while cross-correlations of all kinds of fluctuations for soy bean and soy meal futures are persistent and for corn and wheat futures are anti-persistent in the long term. We also find that cross-correlation exponents are less than the averaged generalized Hurst exponent when q<0$q<0$ and more than the averaged generalized Hurst exponent when q>0$q>0$ in the short term, while in the long term they are almost the same.     

Analysis of birefringence property of three different nematic liquid crystals dispersed with TiO2 nanoparticles

In the present work TiO₂ nanoparticles (NPs) have been dispersed into three different nematic liquid crystals (2020, 1823A and 1550C) in different concentration. The value of the birefringence (Δn) has been calculated by the transmitted intensity method at a 632.8 nm wavelength. NLC 2020 used in the present study is a high birefringent material (Δn = 0.44), NLC 1550C is a low birefringent material (Δn = 0.067) and NLC 1823A is a mid birefringent material (Δn = 0.14). An increased value of birefringence has been found after dispersion of TiO₂ NPs in all three NLCs but this increment depends upon the concentration of the dopant material, temperature range and chemical character of the mixtures. It is suggested that this LC materials can be applicable in making of phase shifters, compensators and many more photonic devices.     

振动诱导液滴与液面不融合现象的研究

发现硅油液滴能够停留在竖直振动的硅油液面上,通过等厚干涉实验说明液滴和液面间存在空气薄膜,分析空气膜形状的变化过程,并依此建立简化模型论述空气膜阻止液滴与液面融合的原理.实验构造了浸没在硅油液面下的硅油液滴,建立理论模型估算空气膜的平均厚度,并与实验估测值对比.本文对多个液滴在液面上呼吸模式的振动现象作了描述和解释.     

Collective excitations of a degenerate gas at the BEC-BCS crossover

We study collective excitation modes of a fermionic gas of (6)Li atoms in the BEC-BCS crossover regime. While measurements of the axial compression mode in the cigar-shaped trap close to a Feshbach resonance confirm theoretical expectations, the radial compression mode shows surprising features. In the strongly interacting molecular BEC regime, we observe a negative frequency shift with increasing coupling strength. In the regime of a strongly interacting Fermi gas, an abrupt change in the collective excitation frequency occurs, which may be a signature for a transition from a superfluid to a collisionless phase.     

Equation of state of hadron resonance gas and the phase diagram of strongly interacting matter

The equation of state of hadron resonance gas at finite temperature and baryon density is calculated taking into account finite-size effects within the excluded-volume model. Contributions of known hadrons with masses up to 2 GeV are included in the zero-width approximation. Special attention is paid to the role of strange hadrons in the system with zero total strangeness. A density-dependent mean field is added to guarantee that the nuclear matter has a saturation point and a liquid-gas phase transition. The deconfined phase is described by the bag model with lowest order perturbative corrections. The phasetransition boundaries are found by using the Gibbs conditions with the strangeness neutrality constraint. The sensitivity of the phase diagram to the hadronic excluded volume and to the parametrization of the mean-field is investigated. The possibility of strangeness-antistrangeness separation in the mixed phase is analyzed. It is demonstrated that the peaks in the K/π and Λ/π excitation functions observed at low SPS energies can be explained by a nonmonotonous behavior of the strangeness fugacity along the chemical freeze-out line. The text was submitted by the authors in English.     

Ultrasonic study on binary liquid mixtures between some bromoalkanes and hydrocarbons

Densities and ultrasound velocities for the binary mixtures of 1-bromobutane+benzene and 1,4-dimethylbenzene and of 1-bromopentane+cyclohexane and benzene have been measured at 308.15 K. Adiabatic compressibilities (beta(ad)), and Wada's constants (W) have also been evaluated as a function of composition. The ultrasound velocities decrease, attains a minimum and then increase with increase in mole fractions of hydrocarbons in the binary mixtures except in the case of 1-bromopentane+benzene binary mixtures where the variation is just the reverse. Dependence of adiabatic compressibilities with mole fractions of hydrocarbons is sigmoid. The non-ideal behaviour of the systems studied is explained on the basis of dipole-induced dipole interactions.     

Formation and decay of hadronic resonances in the QGP

Hadronic resonances can play a pivotal role in providing experimental evidence for partial chiral symmetry restoration in the deconfined quark–gluon phase produced at RHIC and the LHC. Their lifetimes, which are comparable to the lifetime of the partonic plasma phase, make them an invaluable tool to study medium modifications to the resonant state due to the chiral transition. In this Letter we show that the heavier, but still abundant, light and strange quark resonances K^∗$K^{\ast }$, ?, Δ   and Λ^∗${\Lambda }^{\ast }$ have large probability to be produced well within the plasma phase due to their short formation times. We demonstrate that, under particular kinematic conditions, these resonances can be formed and will decay inside the partonic state, but still carry sufficient momentum to not interact strongly with the hadronic medium after the QCD phase transition. Thus, K^∗$K^{\ast }$, ?, Δ   and Λ^∗${\Lambda }^{\ast }$ should exhibit the characteristic property modifications which can be attributed to chiral symmetry restoration, such as mass shifts, width broadening or branching ratio modifications.     

基于香蕉形液晶分子自组装的纳米螺旋丝有机凝胶及其流变特性

在香蕉形液晶分子B4相态中,非手性香蕉形液晶分子自组装形成层状结构,分子在层内倾斜,形成层手性和自发极化,并且造成层内不匹配,最终形成纳米螺旋丝.本文设计了NOBOW/十六烷混合体系,在高温时,香蕉形液晶分子溶解于十六烷,在低温时,香蕉形液晶分子自组装形成纳米螺旋丝,并最终形成三维网络,变成有机凝胶.为深入理解纳米螺旋丝有机凝胶的特性,拓展其在软物质领域的应用,本文通过流变实验对该有机凝胶的黏弹性质进行了系统研究.实验表明纳米螺旋丝有机凝胶与传统凝胶不同,纳米螺旋丝有机凝胶可以随温度变化形成凝胶-流体的可逆变化,并且通过测量NOBOW/十六烷混合体系在不同液晶分子浓度、温度、应变大小和应变速率下的流变特征,揭示了该有机凝胶的流变特性与纳米螺旋丝的性质密切相关.     

Correlation between the molecular chirality index and the spontaneous polarisation in series of smectic C* liquid crystals

A correlation between spontaneous polarisation and the chirality index of the constituent molecules, multiplied by the molecular transverse dipole, has been considered for five series of ferroelectric smectic C* liquid crystals. A good correlation has been found within each series, and it has been shown that the scaled chirality index may be used to estimate the spontaneous polarisation in a series of smectic C* mesogens with small systematic changes of the molecular structure. At the same time one cannot expect any significant correlation between the polarisation and the chirality index for smectic C* materials of sufficiently different structure because the spontaneous polarisation may be significantly effected by some details of the molecule's structure including the orientation of the transverse dipole with respect to the primary short molecular axis.     

Momentum distribution and condensate fraction of a fermion gas in the BCS-BEC crossover

By using the diffusion Monte Carlo method we calculate the one- and two-body density matrix of an interacting Fermi gas at T = 0 in the BCS to Bose-Einstein condensate (BEC) crossover. Results for the momentum distribution of the atoms, as obtained from the Fourier transform of the one-body density matrix, are reported as a function of the interaction strength. Off-diagonal long-range order in the system is investigated through the asymptotic behavior of the two-body density matrix. The condensate fraction of pairs is calculated in the unitary limit and on both sides of the BCS-BEC crossover.     

Collective modes and ballistic expansion of a fermi gas in the BCS-BEC crossover

We evaluate the frequencies of collective modes and the anisotropic expansion rate of a harmonically trapped Fermi superfluid at varying coupling strengths across a Feshbach resonance driving a BCS-BEC crossover. The equations of motion for the superfluid are obtained from a microscopic mean-field expression for the compressibility and are solved within a scaling ansatz. Our results confirm nonmonotonic behavior in the crossover region and are in quantitative agreement with current measurements of the transverse breathing mode by Kinast et al. [Phys. Rev. Lett. 92, 150402 (2004)]] and of the axial breathing mode by Bartenstein et al. [Phys. Rev. Lett. 92, 203201 (2004)]].     

A relation between X-ray diffraction based liquid structure and packing coefficient

A relation between the liquid structure and the molecules packing coefficient has been derived on the grounds of the experimental results of X-ray diffraction studies. The packing coefficientk was assumed to be a criterion of correctness of the structural models of 2-methyl-1-propanol and 2-methyl-2-propanol based on experimental results. This coefficient was estimated from the specific volumes of moleculesV ₀, volumes of elementary pseudocellsV and the number of molecules comprised into these pseudocells. The volumesV of pseudocells were estimated from the same X-ray diffraction pattern as was used for determination of the liquid structure. The determined values of the packing coefficient support the chain-like structure of associates of liquid 2-methyl-1-propanol and reject the chain-like structure for liquid 2-methyl-2-propanol.     

Quantum phase transition between a Luttinger liquid and a gas of cold molecules

We consider cold polar molecules confined in a helical optical lattice similar to those used in holographic microfabrication. An external electric field polarizes molecules along the axis of the helix. The large-distance intermolecular dipolar interaction is attractive but the short-scale interaction is repulsive due to geometric constraints and thus prevents collapse. The interaction strength depends on the electric field. We show that a zero-temperature second-order liquid-gas transition occurs at a critical field. It can be observed under experimentally accessible conditions.