共查询到18条相似文献,搜索用时 125 毫秒
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基于Dyson-Schwinger方程(DSEs)所确定的夸克传播子和算符成积展开(OPE),在彩虹近似下,预言了QCD真空中非定域夸克真空凝聚的结构。这种结构由夸克自能函数Af和Bf决定,通过数值求解DSEs就可以得到这些自能函数。但是,直接数值求解DSEs方程非常复杂,这里采用Roberts和Williams提出的参数化方法,用参数化的夸克传播函数σf v(p2)和σf s(p2)计算夸克自能函数。同时,也计算了定域的夸克真空凝聚值,夸克胶子混合的真空凝聚值,以及夸克的虚度。理论预言和计算结果均与标准QCD求和定则、格点QCD和瞬子模型的理论结果大致相符。和这些模型的结果相比,参数化方法得到的轻夸克(u,d,s)的定域真空凝聚偏大,这主要是由于模型依赖导致的。与u,d夸克相比,s夸克的真空凝聚比较大,这是因为s夸克自身质量较大的缘故。当然,Roberts-Williams参数化的夸克传播子只是一个经验公式,只能近似描述夸克的传播。 相似文献
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基于夸克传播子的Dyson-Schwinger方程,计算了夸克胶子混合真空凝聚和夸克真空凝聚. 这些凝聚不仅联系着夸克在真空态中的虚度,而且也表征了真空中夸克分布的空间宽度. 真空凝聚的存在直接反映着QCD真空的非微扰结构. 计算表明:上夸克与下夸克的虚度为λ2u,d=0.7GeV2,奇异夸克的虚度为λ2s=1.6GeV2. 这些结果与许多用完全不同的方法得到的结果一致. 相似文献
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基于Dyson Schwinger方程和彩虹近似 ,我们导出了完全穿衣服 (fullydressed)的夸克传播子。利用所得到的夸克传播子 ,研究了非定域的夸克真空凝聚的结构 ,成功地预言了定域的夸克真空凝聚值和夸克胶子的混合真空凝聚值。理论预言的凝聚值与文献中常用的经验值完全一致。 相似文献
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本文讨论了QCD真空凝聚效应对强子结构函数中R比值(R≡σL/σI)的影响.利用背景场的基本思想,本文从有效拉氏量出发,计算了夸克凝聚对R比值的非微扰修正(Q-2项).结果显示本文所给出的修正在小x区较敏感. 相似文献
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格点(1+1)维QCD中<ψψ>的变分研究 总被引:1,自引:1,他引:0
改进的哈密顿量对格点(1+1)维QCD中Wilson费米子真空凝聚<ψψ>做变分研究.结果不但与连续理论的预言值一致,而且几乎不依赖于Wilson参数r.对于改进的哈密顿量而言,么正变换算符中的三链项对<ψψ>的贡献是很重要的. 相似文献
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讨论夸克凝聚和混合凝聚在Lorentz规范下的泰勒展开式,这两个展开式可用来计算算符乘积展开中非微扰修正项的Wilson系数.与目前在QCD求和规则方法中所应用的、在固定点规范下的相应展开式相比,新的展开式具有平移不变性的优点. 相似文献
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ZHOU Li-Juan GU Yun-Ting MA Wei-Xing MENG Cheng-Ju PAN Ji-Huan 《理论物理通讯》2008,49(1):181-188
Based on the Global Color Symmetry Model, the non-perturbative Q, CD vacuum is investigated in the parameterized fully dressed quark propagator. Our theoretical predictions for various quantities characterized the QCD vacuum are in agreement with those predicted by many other phenomenologieal QCD inspired models. The successful predictions clearly indicate the extensive validity of our parameterized quark propagator used here. A detailed discussion on the arbitrariness in determining the integration cut-off parameter ofμ in calculating QCD vacuum condensates and a good method, which avoided the dependence of calculating results on the cut-off parameter is also strongly recommended to readers. 相似文献
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We study the properties of QCD vacuum state in this paper. The values of various local quark vacuum condensates, quark-gluon mixed vacuum condensates, and the structure of non-local quark vacuum condensate are predicted by the solution of Dyson-Schwinger Equations in "rainbow" approximation with three sets of different parameters for effective gluon propagator. The light quark virtuality is also obtained in a consistent way. Our all theoretical results here are in good agreement with the empirical values used widely in literature and many other theoretical calculations. 相似文献
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Based on Dyson-Schwinger equations in “rainbow“ approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other. 相似文献
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According to extensive study of the Dyson-Schwinger equations for a fully dressed quark propagator in the "rainbow" approximation with an effective gluon propagator, a parametrized fully dressed confining quark propagator is suggested in this paper. The parametrized quark propagator describes a confined quark propagation in hadron, and is analytic everywhere in complex p2-plane and has no Lehmann representation. The vector and scalar self-energy functions [1 - Af(p2)] and [Bf(p2) - mf], dynamically running effective mass of quark Mf(p2) and the structure of non-local quark vacuum condensates as well as local quark vacuum condensates are predicted by use of the parametrized quark propagator. The results are compatible with other theoretical calculations. 相似文献
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研究夸克的质量是QCD研究中的一个非常重要问题。因为, 夸克质量是标准模型的基本输入参数, 准确地确定这些参数无论对于唯象的应用还是对于理论的应用都是极其重要的。基于参数化的完全穿衣服的夸克传播子, 研究了自能函数和夸克的动力学质量。理论预言了夸克质量和自能函数, 其结果与文献中的经验值相符合, 也与Dyson Schwinger方程解一致。反过来这也说明了参数化的夸克传播子是成功和可靠的。Study of mass of quark is one of the most important issues in the investigation of QCD. Because masses of quarks are fundamental QCD input parameters of standard Model, and an accurate determination of these parameters is extremely important for both phenomenological and theoretical applications. Based on the parameterized fully dressed quark propagator proposed by us, the theoretical predictions of the masses of quarks are predicted in this short note. The effective quark mass is defined by the scalar self energy function Bf(p2) and vector self energy function Af(p2). The results of our calculations are in agreement with the empirical values used widely in literature and also show that the parameterized form of quark propagator is an applicable and reliable approximation. 相似文献
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Spontaneous breaking of chiral symmetry is investigated in the Hamiltonian approach to QCD in Coulomb gauge. The quark wave functional is determined by the variational principle using an ansatz which goes beyond the commonly used BCS-type of wave functionals and includes the coupling of the quarks to the transversal spatial gluons. Using the lattice gluon propagator as input it is shown that the low energy chiral properties of the quarks, like the quark condensate and the constituent quark mass, are substantially increased by the coupling of the quarks to the spatial gluons. Our results compare favorably with the phenomenological values. 相似文献