Quark Number Susceptibility around the Chiral Critical End Point

We calculate the quark number susceptibility （QNS） around the chiral critical end point （CEP）. The CEP is found to be located at （μc,Tc）= （80 MeV, 148 MeV） where μc and Tc are the critical chemical potential and temperature, respectively. The QNS is found to have the highest and sharpest peak at the CEP. It is also found that, when the chemical potential μ is in the range of 60MeV≤ μ ≤ 110MeV, the QNS near the transition temperature is larger than the free field result, which indicates that the space-like damping mode dominates the degree of freedom of motion near the CEP.

Locating the QCD critical end point through peaked baryon number susceptibilities along the freeze-out line

We investigate the baryon number susceptibilities up to fourth order along different freeze-out lines in a holographic QCD model with a critical end point（CEP）, and we propose that the peaked baryon number susceptibilities along the freeze-out line can be used as a clean signature to locate the CEP in the QCD phase diagram.On the temperature and baryon chemical potential plane, the cumulant ratio of the baryon number susceptibilities（up to fourth order） forms a ridge along the phase boundary, and develops a sword-shaped ＂mountain＂ standing upright around the CEP in a narrow and oblate region. The measurement of baryon number susceptibilities from heavy-ion collision experiments is along the freeze-out line. If the freeze-out line crosses the foot of the CEP mountain, then one can observe the peaked baryon number susceptibilities along the freeze-out line, and the kurtosis of the baryon number distributions has the highest magnitude. The data from the first phase of the beam energy scan program at the Relativistic Heavy Ion Collider indicates that there should be a peak of the kurtosis of the baryon number distribution at a collision energy of around 5 Ge V, which suggests that the freeze-out line crosses the foot of the CEP mountain and the summit of the CEP should be located nearby, around a collision energy of 3–7 GeV.

重离子碰撞中守恒荷涨落与QCD相变的输运模型研究

相对论重离子对撞机(Relativistic Heavy Ion Collider,RHIC)-STAR(Solenoid Tracker at RHIC)实验测量了√s_(NN)=7.7~200 GeV能量下Au+Au碰撞中的净质子(净重子的代表)、净电荷和净K介子(净奇异数的代表)多重数分布的累积量,发现净质子四阶累积量与二阶累积量之比(κσ^(2))呈现出了非单调的能量依赖性行为。在相对论重离子碰撞实验中只能测到末态粒子的信息。因此,基于多相输运(A Multi-Phase Transport,AMPT)模型对Au+Au碰撞系统中守恒荷(重子数、电荷数和奇异数)的涨落性质进行了研究,发现AMPT模型的结果基本能描述RHIC-STAR实验结果。更重要的是,利用AMPT模型了解了相对论重离子碰撞动力学演化过程中几个关键效应(守恒荷粒子的产生和扩散、强子化、强子再散射和弱衰变)对守恒荷涨落演化及其粒子关联函数的影响。发现正负电荷之间关联可能源于弦熔化机制,重子(质子)关联函数符合重子数守恒期望,奇异数(净K介子)的关联函数源于对产生,这些代表量与守恒荷的对应关系行为上定性一致,但数量不同。虽然AMPT模型目前缺乏临界涨落机制,但我们的结果可以为守恒荷涨落的研究提供一条基线,这有助于在相对论重离子碰撞中寻找量子色动力学(Quantum Chromodynamics,QCD)临界点(Critical End Point,CEP)附近可能的临界行为。初步在模型中考虑临界密度涨落,结果发现它起着一定的作用。

临界现象与泛函重整化群

本文主要介绍了近年来泛函重整化群(FunctionalRenormalizationGroup,f RG)在量子色动力学(Quantum Chromodynamics,QCD)相变及其临界现象研究中的一些进展,主要侧重于与QCD的临界终点(Critical End Point,CEP)相关的非微扰临界指数的计算、重子数的涨落等。fRG是一种非微扰连续场论的理论方法,其基本思想是通过重整化群能标从高能向低能的演化,连续不断地将不同尺度的量子涨落以及热涨落积分到理论体系当中。本文讨论了非微扰有效势重整化群流方程和不动点方程的各种求解方法,包括泰勒展开、空间维数ε=4-d展开以及最近被提出的非局域势直接求解方法。还系统地讨论了与QCD的临界终点等临界现象密切相关的重子数的涨落,探讨了实验观测到的净质子数分布的峰度,也就是四阶矩随碰撞能量非单调依赖关系的可能原因。

QCD临界终点与重子数扰动

相对论性重离子对撞的目的之一是寻找量子色动力学(Quantum Chromodynamics,QCD)临界终点(Critical End Point,CEP),实验中测到的净质子数扰动呈现出非单调的行为,这暗示了CEP的存在。本文使用了3味PNJL(Polyakov-loop Nambu-Jona-Lasinio)模型,沿着从实验数据中拟合的化学冻结线,计算了重子数扰动累积量之比C4/C2随对撞能量的变化。结果发现,基于平衡态假设,在对撞能量7.7~200 GeV范围内,随着对撞能量的降低,C4/C2先缓慢下降后上升,这与实验数据一致。这也暗示平衡态假设可以用于探索重离子对撞后系统的演化行为,揭示了相变线跟化学冻结线的关系对观测量的影响非常重要。

The entanglement properties of holographic QCD model with a critical end point

We investigated different entanglement properties of a holographic QCD(hQCD)model with a critical end point at the finite baryon density.Firstly,we considered the holographic entanglement entropy(HEE)of this hQCD model in a spherical shaped region and a strip shaped region.It was determined that the HEE of this hQCD model in both regions can reflect QCD phase transition.Moreover,although the area formulas and minimal area equations of the two regions were quite different,the HEE exhibited a similar behavior on the QCD phase diagram.Therefore,we assert that the behavior of the HEE on the QCD phase diagram is independent of the shape of the subregions.However,the HEE is not an ideal parameter for the characterization of the entanglement between different subregions of a thermal system.As such,we investigated the mutual information(MI),conditional mutual information(CMI),and the entanglement of purification(Ep)in different strip shaped regions.We determined that the three entanglement quantities exhibited some universal behavior;their values did not change significantly in the hadronic matter phase but increased rapidly with the increase in T andμin the QGP phase.Near the phase boundary,these three entanglement quantities changed smoothly in the crossover region and continuously but not smoothly at CEP;they exhibited discontinuous behavior in the first phase transition region.These properties can be used to distinguish between the different phases of strongly coupled matter.

稻谷中脂肪酸值的测定及关键点控制的探索

脂肪酸值是反映稻谷品质优劣的主要指标,是判定稻谷储存品质的主要依据之一,对粮食收购、储备、加工和食用均有重要意义。因此,为了准确测定稻谷中的脂肪酸,必须把握好稻谷中脂肪酸值测定过程的关键控制点,特别是对于滴定终点的判定。

浅析年终奖的个人所得税临界点及运用

本文简要分析年终一次性奖金在个人所得税计算时的临界点,并进一步分析在考虑个人所得税临界点的前提下,如何进行纳税筹划。

关于新一轮个人所得税调整的思考——工资薪金改革角度的探讨

近些年以来,个人所得税的改革一直都是大众所关心的话题。本文首先对此次新一轮个人所得税的改革做一个简单的回顾,通过较为详细的数据对比,分析了年终奖在缴纳个人所得税时,存在奖金增加反而税后收入减少的现象,然后以新、旧个人所得税法间的比较为出发点,对新个人所得税法可能产生的诸多影响进行简单的探讨。

电弧炉炼钢过程钢中临界碳的实测和脱碳操作实践

经测试得出 ,在临界 [C]为 0 .2 %～ 0 .8%、供氧强度为定值时 ,脱碳速度主要取决于 [C]向钢渣反应界面的扩散。 70tUHPDC电弧炉脱碳实践表明 ,采用熔清后全程小角度吹氧 ,熔池沸腾良好后再喷碳粉造泡沫渣 ,渣碱度为 2 .0～ 2 .5 ,避免形成低碱度泡沫渣 ,在临界 [C]范围内进行通电脱碳操作 ,利用电路磁场搅拌作用 ,促进 [C]向反应界面扩散 。

关于图中非临界点的个数

设C为简单非完全图,连通度为H,r(G)为G中非临界点的个数。证明了当时当:时当时其中A为偶数h为奇数并且上述下界是最佳的。

量子色动力学在有限温度密度区间的相结构(英文)

本文综述量子色动力学在有限温度密度区间的相结构,包括高密条件下的色超导态和在高温条件下相对论重离子碰撞实验中产生的强耦合夸克-胶子等离子体。我们简要地介绍在相对论重离子碰撞实验中发现强耦合夸克-胶子等离子体的历史,并且讨论用体粘滞系数与熵的比值确定QCD临界点的可能性。对于在高密区域的相结构,我们着重讨论错位配对情况下的非标准色超导态,解释无能隙色超导态的色磁不稳定性、Sarma不稳定性和Higgs不稳定性.

超临界机组汽轮机低压缸叶片腐蚀案例及原因分析

超临界机组大修检查普遍发现汽轮机低压缸叶片存在点蚀现象。为了分析低压缸叶片点蚀的产生原因,采用扫描电镜、能谱仪对腐蚀产物进行了分析,采用离子色谱仪对机组水汽进行了检测。结果表明:水汽中CO_(2)含量很少,对叶片点蚀的影响不大;点蚀主要原因是精处理混床运行终点控制不当,造成水汽中氯离子含量偏高所致。控制好精处理混床运行终点,可以有效避免超临界机组汽轮机低压缸叶片的点蚀问题。

Characterizing variable for the critical point in momentum space

The possible experimentally observable signal in momentum space for the critical point, which is free from the contamination of statistical fluctuations, is discussed. It is shown that the higher order scaled moment of transverse momentum can serve as an appropriate signal for the critical point, provided the transverse momentum distribution has a sudden change when energy increases passing through this point. A 2-D percolation model with a linear temperature gradient is constructed to check this suggestion. A sudden change of third order scaled moment of transverse momentum is observed.

年终奖个人所得税纳税筹划

当前,我国很多单位在做发放年终一次性奖金的决策时,一般较少考虑个人所得税的纳税问题。文章就年终一次性奖金发放的税务筹划临界点、无效发放区间和低效发放区间进行计算分析,从而对年终奖金的个人所得税进行纳税筹划。

Reconstruction of baryon number distributions

The maximum entropy method(MEM)and Gaussian process(GP)regression,which are both well-suited for the treatment of inverse problems,are used to reconstruct net-baryon number distributions based on a finite number of cumulants of the distribution.Baryon number distributions across the chiral phase transition are reconstructed.It is deduced that with the increase of the order of cumulants,distribution in the long tails,i.e.,far away from the central number,would become increasingly important.We also reconstruct the distribution function based on the experimentally measured cumulants at the collision energy sNN−−−√=7.77 GeV.Given the sizable error of the fourth-order cumulant measured in the experiments,the calculation of MEM shows that with the increasing fourth-order cumulant,there is another peak in the distribution function developed in the region of the large baryon number.This unnaturalness observed in the reconstructed distribution function could in turn be used to constrain the cumulants measured in the experiments.

利用格点量子色动力学研究手征平滑过渡温度和手征相变温度

回顾了最近关于手征平滑过渡温度和手征相变温度的研究结果。首先给出了在零重子化学势能下的手征平滑过渡温度为156.5(1.5)MeV,其次,给出了在非零重子化学势能下手征相转变曲线的二阶及四阶曲率分别为0.012(4)和0.000(4)。接着讨论了在格点QCD中第一次得到的量子色动力学的手征相变温度。在热力学极限、连续极限及手征极限下,我们得到手征相变温度为132_(-6)^(+3)MeV。

Chiral phase transition and equation of state in chiral imbalance

The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model.In this newly developed model,modifications to the chemical μand chiral chemical μ5 potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian.In the proper-time scheme,the chiral phase transition is a crossover in the T-μ plane.However,when μ5 is incorporated,our study demonstrates that a first order phase transition may emerge.Furthermore,the chiral imbalance will soften the equation of state of quark matter.The mass-radius relationship and tidal deformability of quark stars are calculated.The maximum mass and radius decrease as μ5 increases.Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state.

120t VOD冶炼水轮机用钢ZG06Cr13Ni4Mo的生产实践

根据真空下"脱碳保铬"的热力学、动力学理论,对上海某铸造厂冶炼ZG06Cr13Ni4Mo钢的生产进行了研究。结果表明,通过观察固体氧浓差电池测定气相中氧分压电势值的变化曲线及尾气温度变化情况,能准确判断120 t VOD吹炼过程中碳的临界值、氧化终点,从而实现真空下"脱碳保铬"的有效控制。

改进的PNJL模型下QCD的相图

Polyakov-Nambu-Jona-Lasinio(PNJL)模型是研究强相互作用物质性质的使用最为广泛的有效模型之一。在PNJL模型的基础上考虑了手征凝聚和Polyakov圈之间的纠缠作用,并且引入了化学势修正的Polyakov有效势,由此得到了化学势依赖的entangled PNJL(μEPNJL)模型。在平均场框架下的计算结果表明:相较于原始的PNJL模型,由μEPNJL模型计算得到的临界点(CEP)朝着温度更高、化学势更小处移动,并且手征对称性恢复相变和退禁闭相变在较大的化学势范围内都重合得很好。通过与STAR合作组在相对论重离子对撞机(RHIC)上进行的净质子数分布的测量结果相比,可以发现,通过适当的参数调节,由μEPNJL模型计算得到的CEP更加靠近实验预言的CEP可能存在的区域。