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1.
利用3个不同的初始手征角,给出了重子数为1的体系的平均场方程的一次迭代后的解,以此研究哪一种手征角可以令平均场方程的解的自洽性更快地达到。对于不同的初始手征角,发现经过第一次迭代后,指数形式的手征角给出的结果比别的手征角更接近自洽解的形状。  相似文献   

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3.
对称性及其破缺是基本的科学问题。手征对称性在自然界中广泛存在,大至星系旋臂、行星自转,小到矿物晶体、有机分子、基本粒子,都与手征对称性密切相关。原子核层次的手征对称性概念于1997年提出,随后成为核物理研究的热点问题。目前,实验上已经在核素图上的80,100,130和190质量核区发现了30多例可能具有手征对称性的原子核。简要介绍原子核中的手征对称性概念;手性原子核的预言、识别以及实验验证;并通过展示手性原子核结构的多样性(MχD),回顾了理论和实验研究进展;介绍最新发现的原子核中手性和空间反射对称性的联立自发破缺,对未来手性原子核研究的前景进行了展望。Symmetry and its breaking are basic scientific problems. Chiral symmetries are common in nature, for example, the macroscopic spiral arms of galaxies and the rotation of planets; the microscopic spirals of the mineral crystalline, the organic molecules and the elementary particles. The concept of chirality in atomic nuclei was first proposed in 1997. Since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Up to now, more than 30 candidates of chiral nuclei have been reported in the 80, 100, 130, and 190 mass regions. The concept of the chirality in atomic nuclei, the prediction, the signal, and the experimental verification of the chiral nuclei are briefly introduced; the recent theoretical and experimental progress are reviewed, in particular the existence of multiple chiral doublets (MχD), i.e., more than one pair of chiral doublet bands in one single nucleus; the simultaneous spontaneous breaking of chiral and reflection symmetry in the newly observed atomic nuclei is introduced, together with a prospect on the future study on nuclear chiral symmetry.  相似文献   

4.
三维QED 具有两个和QCD类似的性质:动力学手征对称破缺和禁闭。为了研究动力学手征对称破缺,基于彩虹近似,在Dyson-Schwinger 方程框架下,通过迭代求解有限温下的费米子自能方程,讨论了不同的费米速度下费米子手征凝聚与费米子味数之间的关系。发现在有限温下,对于固定的费米子味数,费米手征凝聚随费米速度的变大而单调减小。Analogous to Quantum QCD, QED3 has two interesting features: dynamical chiral symmetry breaking (DCSB) and confinement. By adopting the rainbow approximation, we numerically solve the fermion self-energy equation at finite temperature in the framework of Dyson-Schwinger equations and discuss the relation between chiral condensate and fermion flavor for several fermion velocities in the finite temperature QED3. It is found that the fermion chiral condensate decreases monotonically with the fermion velocity increasing for a fixed N at finite temperature.  相似文献   

5.
相对论重离子碰撞的拓扑荷作用破坏作用平面两侧不同手征性的夸克数目的平衡,从而引起P和CP破坏特征。本工作主要分析RHIC和LHC能区的手征电荷分离作用,分析手征电荷分离随碰撞中心度、碰撞能量和核屏蔽等依赖关系。并未发现手征电荷分离效应与碰撞能量大小有非常紧密的依赖关系,但发现核屏蔽效应对手征电荷分离有重要的影响,与不考虑屏蔽效应相比,考虑屏蔽效应会使手征分离效应明显压低,由于屏蔽效应出现,使得a++a--)的分布与a+-a-+)分布并不对称。并且还发现手征分离效应主要发生在碰撞参量较大的周边碰撞,越接近中心碰撞,手征分离效应几乎可以忽略。The topological charge interactions in relativistic heavy ion collisions cause quark chirality imbalance, resulting in charge separation under the strong magnetic field and local P and CP violation. In this paper, the chiral charge separation at RHIC and LHC energies is systematically analyzed as functions of the collision centrality, the collision energy and the nuclear shielding factor. It is found that there is not a very close dependence of the chiral charge separation effect on the collision energies, but that has an important dependence on nuclear shielding factor. Compared with the non-shielding effect, the shielding effect can reduce the chiral separation effect obviously. Due to the shielding effect, the distribution of a++(a--) and the distribution of a+-(a-+) are asymmetric. One also finds that chiral separation effect, which is almost negligible when more close to the central collision, occurs mainly in the peripheral collision for larger impact parameter.  相似文献   

6.
采用手征σ模型描述核多体系统,考虑真空极化的影响,首先由核物质的饱和性质确定模型参数,进一步研究了强子性质在核介质中的变化。手征σ模型的研究结果给出,核子和ω介子的有效质量随核物质密度的增大而减小,但σ介子的有效质量随密度的增大而增大。这些结果与不满足手征对称性的Walecka模型结果进行了比较。计算中采用的重整化方法会对结果有一定的影响。The modification of hadron masses in nuclear medium is studied by using the chiral sigma model, which is extended to generate the omega meson mass by the sigma condensation in the vacuum in the same way as the nucleon mass. The chiral sigma model provides proper equilibrium properties of nuclear matter. It is shown that the effective masses of both nucleons and omega mesons decrease in nuclear medium, while the effective mass of sigma mesons increases at finite density in the chiral sigma model. The resuits obtained in the chiral sigma model are compared with those obtained in the Walecka model, which includes sigma and omega mesons in a non-chiral fashion.  相似文献   

7.
核物理中的手征微扰论   总被引:1,自引:1,他引:0  
手征微扰论是基于量子色动力学的低能有效理论 ,已成为核物理和低能粒子物理研究的有力方法 .简单介绍了手征微扰论的基本概念、方法和应用 ,特别是近年来重子手征微扰论的形式发展和一些应用中的前沿问题. Chiral Perturbation Theory (CHPT), as a low-energy effective field theory based on QCD, is a powerful tool in the investigation of the nuclear and particle physics. We present an introduction to the basic idea, the method and the application of CHPT, and emphasize the recent development in the formalism and the application of baryon CHPT.  相似文献   

8.
讨论了在LHC的Pb-Pb碰撞过程中,如果QGP SU(2)手征相变出现二级相变,那么系统将会有π弦产生,并且π弦最终将衰变为π介子。于是以上效应将导致在低动量区域(p~150—400 MeV)内的π介子增强。对应于不同的冷却温度Tf=130,120,110 MeV,产生于π弦衰变的π介子的数量分别是Nt≈270,150, 60. It is pointed out that if the QGP SU(2) chiral phase transition in the LHC Pb Pb collision process is taken place and the phase transition is in the second order, then pion strings will be formed, and decay. These phenomena lead to the pion enhancement in the low momentum region(p150—400 MeV) and the number of pions produced from pion string decay can be estimated about Nt≈270, 150, 60 for different freeze temperature Tf=130, 120, 110 MeV respectively.  相似文献   

9.
总结和系统介绍了磁转动物理领域的新进展 .阐述了剪刀带的形成机制 ,并论证了在半经典近似和平均场近似下 ,倾斜轴推转模型与粒子转子模型等价 .讨论了原子核在有三轴形变时出现的一种全新的磁转动现象——手征双重带 .并从对称性的角度讨论了剪刀带及手征双重带的能谱特征 .给出了实验上可能存在磁转动带的核区.A new interesting field —— magnetic rotation physics is reviewed. It is proved that the tilted axis cranking (TAC) model is equivalence to the particle rotor model (PRM) under the semi classical and mean field approximations. The shears mechanism and the new discovered phenomena in triaxial deformed nuclei—— chiral doublets are discussed. The possible mass region for these magnetic rotation phenomena is presented.  相似文献   

10.
用手征 SU( 3)夸克模型分析了 ( 0 s) 6组态的六夸克态能量 ,结果表明手征 SU( 3)介子场可以对某些多奇异数的态提供较强的吸引作用 .进一步用共振群方法研究了 ( ΩΩ) 0 + 及 ( ΩΞ) 1+ 等多奇异数系统 ,得到 ( ΩΩ) 0 是一个深度束缚的双重态. An analysis is made for the (0s) 6 six quark cluster states in the chiral SU (3) quark model. The results show that for some multistrangeness states the chiral SU (3) could offer more attraction. Further RGM dynamical calculation of the multistrangeness system (ΩΩ) 0+ and (ΩΞ) 1+ has been done. It shows that (ΩΩ) 0+ is a deeply bound state in the chiral SU (3) quark model.  相似文献   

11.
部分填充手征等离子体波导的电磁波   总被引:1,自引:1,他引:0       下载免费PDF全文
 把麦克斯韦方程和电磁场分解成横向和纵向分量, 导出了简明的一般性的手征等离子体填充的任意截面波导的波动方程和横向纵向场的关系式。对于部分填充手征等离子体波导, 导出了它的色散方程。这一方程的数值解给出了HE11, EH01和HE21模式的色散图。随着手征等离子体填充面积的增大, EH01模式的色散曲线向更高的频率移动。随着手征导纳的增加, 传播常数减小。  相似文献   

12.
手征参数对光纤中模式特性的影响   总被引:10,自引:2,他引:8  
董建峰 《光学学报》1997,17(4):76-481
对圆芯和包层都是手征介质的阶跃型手征光纤进行了解析求解,导出了模式特征方程,给出了手征光纤中模式场,光强和光功率分布的表达式。分别研究了纤芯和包层中的手征参数对模式特性的影响.。  相似文献   

13.
原子核的手征对称性和空间反射对称性研究是近来原子核结构研究的前沿热点问题,吸引了大量的实验和理论研究。通过在束伽玛谱学的实验方法,在原子核78Br中发现了两对宇称相反的手征双重带,以及它们之间表征八极关联的电偶极跃迁。这是首次在原子核中发现了八极关联的多重手征带,给出了原子核存在手征对称性和空间反射对称性联立自发破缺的实验证据。Spontaneous symmetry breaking is a fundamental concept in nature. Chiral Symmetry Breaking and reflection-asymmetry in nuclei has been a subject of intensive experimental and theoretical investigation. Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive-and negative-parity bands have been identified in 78Br by means of in-beam gamma-ray spectroscopy techniques. These four rotational bands are suggested as multiple chiral doublet bands with octupole correlations. This observation indicates that nuclear chirality can be robust against the octupole correlations. It is of highly scientific interest to search for the chirality-parity quartet bands in nucleus with both stable triaxial and octupole deformations.  相似文献   

14.
手征(chiral)概念是许多科学领域所关注的焦点,其研究也是探索生命起源和生命活动最吸引人的研究方向之一。本简要介绍近几年基于极化电子散射实验的分子手征效应研究的实验方法及结果,并展望了该领域的实验发展前景,以希望能在高灵敏度及新实验方法基础上更深入研究手征效应的物理内容。  相似文献   

15.
介绍了两个近期基于协变手征微扰理论构建领头阶核子-核子和超子-核子相互作用的工作。理论中未知的低能常数通过拟合核子-核子和超子-核子散射实验数据确定。分析发现,在对散射数据的描述上,领头阶相对论手征力可以媲美次领头阶非相对论手征核力。研究表明,构建相对论手征重子-重子相互作用技术上是可行的。得到的相互作用不仅可以为相对论核结构及反应研究提供重要的理论输入,而且可以进一步加深对低能强相互作用的认识。In this paper, we report on two recent studies of relativistic nucleon-nucleon and hyperonnucleon interactions in covariant chiral perturbation theory, where they are constructed up to leading order. The relevant unknown low energy constants are fixed by fitting to the nucleon-nucleon and hyperon-nucleon scattering data. It is shown that these interactions can describe the scattering data with a quality similar to their next-to-leading order non-relativistic counterparts. These studies show that it is technically feasible to construct relativist baryon-baryon interactions, and in addition, after further refinements, these interactions may provide important inputs to ab initio relativistic nuclear structure and reaction studies and help improve our understanding of low energy strong interactions.  相似文献   

16.
手征(chiral)概念是许多科学领域所关注的焦点,其研究也是探索生命起源和生命活动最吸引人的研究方向之一.本文简要介绍近几年基于极化电子散射实验的分子手征效应研究的实验方法及结果,并展望了该领域的实验发展前景,以希望能在高灵敏度及新实验方法基础上更深入研究手征效应的物理内容.  相似文献   

17.
椭圆芯手征光纤的基模特性研究   总被引:4,自引:1,他引:3  
董建峰 《光学学报》1998,18(10):385-1389
对椭圆芯手征光纤进行了严格的求解,得到了模式场的解析解;推了了模式特征方程;并对基模的偶模和奇模特征方程进行数值求解,研究了手征参数对不同椭圆比下基模的色散曲线,双折射,模间色散等特性的影响。  相似文献   

18.
美国的布鲁克海文国家实验室相对论重离子对撞机(RHIC)和欧洲核子中心的大型强子对撞机(LHC)的大量实验结果表明,在相对论重离子碰撞中已经产生了一种近似完美流体的强耦合部分子物质。基于一个多相粒子输运模型(AMPT)理论工具,对RHIC和LHC实验上的一些重要结果的开展了三个方面的理论研究工作(集体流、喷注淬火、手征磁效应),研究结果揭示了初始的夸克胶子等离子体(QGP)能量密度涨落经过部分子输运演化产生末态粒子的各阶次的集体流、喷注和部分子物质的相互作用导致喷注的能量损失、末态相互作用严重影响手征磁效应的大小等物理过程作用机制。The experimental results from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) show that a nearly perfect fluid (i.e. strong-coupling Quark Gluon Plasma) has been created in relativistic heavy-ion collisions. I introduce our theoretical results based on a multi-phase transport (AMPT) model. Several important topics such as collective flow, jet quenching, chiral magnetic effect, are addressed. The simulation results indicate that the initial fluctuations of energy density of the QGP lead to all orders of harmonic flows of final particles via parton cascade, the strong interactions between jet and the QGP make jet lose much energy, and the final state interactions play an important role to affect the initial chiral magnetic effect in relativistic heavy-ion collisions.  相似文献   

19.
量子色动力学中夸克和拓扑胶子场的相互作用可以产生局域宇称和共轭电荷宇称不守恒,这也许能解释宇宙中物质-反物质的不对称性。在强磁场下,宇称不守恒会导致粒子按正负电荷分离,此现象称为手征磁效应。在重离子碰撞实验中对电荷分离的测量主要受物理本底的影响,大部分的理论和实验工作一直致力于消除或减少这些本底。在此综述了相对论重离子碰撞中手征磁效应寻找的现状。Quark interactions with topological gluon fields in QCD can yield local P and CP violations which could explain the matter-antimatter asymmetry in our universe. Effects of P and CP violations can result in charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect (CME). Experimental measurements of the CME-induced charge separation in heavy-ion collisions are dominated by physics backgrounds. Major theoretical and experimental efforts have been devoted to eliminating or reducing those backgrounds. We review the current status of these efforts in the search for the CME in heavy-ion collisions.  相似文献   

20.
首先给出了填充手征媒质的一般柱结构中耦合波方程的解耦过程,然后根据完备本征函数展开对椭圆手征波导中的混合模式进行了详细分析,给出具体的场表达式及色散关系.指出在与椭圆结构相关的耦合问题中,不仅存在TE与TM模式之间的耦合,还存在偶型模与奇型模式的耦合.通过数值计算对椭圆离心率以及手征导纳对色散特性的影响进行了讨论. 关键词: 椭圆手征波导 马丢函数 模式分裂  相似文献   

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