高频波激发低频磁场和离子声波的重整化强湍动理论

本文给出了高温等离子体中高频波激发低频磁场和离子声波强湍动过程的重整化理论,以便改善通常的弱非线性处理方法,从Vlasov-Maxwell方程组出发,在Fourier表象中得到了包含“最发散”和“次发散”效应互相耦合的高频和低频传播于重整化方程组,从而获得了高、低频振荡粒子重整化分布函数和场的耦合关系。在“最发散”重整化近似下,我们求解了高低频传播子方程组,得到了展开到v₄(高频湍动场能密度与等离子体热能密度之比)一次方的近似解和重整化介电函数等表达式。然后,在Fourier逆变换下导得了我们所要的时空表用中重整化强湍动方程组。最后,作为一个说明重整化作用的例子,在一维稳态下求解了孤立子的形式。 关键词：     

无碰撞等离子体的相干重整化理论

本文提出对Власов-Poisson方程进行微扰处理的一种重整化方案。利用图形展开方法证明了该理论到任意阶微扰的可重整化性质。给出了重整化传播量的一般形式。分析了相干项和绝对非相干项的物理意义。给出了重整化介电函数的正确表示,并对它的意义做了讨论。通过和以往重整化理论的比较,指出这种重整化方案是一种真正的完全重整化。 关键词：     

有限温度下胶子场三圈真空图中的红外发散

用热传播子的实时形式对有限温度下胶子场的三圈真空图进行了详细的计算，在维数正规化方案下把真空图中的红外发散全部孤立出来了.     

介子-重子反应中圈积分重整化问题的研究

用手征夸克模型的手征幺正法研究介子-重子S波散射过程中,首要处理的是传播子圈积分的重整化问题。研究发现,在大部分扇区中,采用动量截断法和维数正规化法进行重整化都可适用;但在某些扇区中,动量截断法重整化会使传播子出现"人为奇点",不能适用。     

核场论中声子重整化的初步研究

本文在声子固有自能子图取为图1(1)的情况下,写出了重整化声子的戴逊方程,得到了重整化声子的本征方程,以及声子和规则与声子权重能量和规则。     

标准模型中两类中性玻色子混合圈链图传播子的重整化及其e+e-→μ+μ-反应截面

采用电弱统一标准模型, 对光子γ和中间玻色子Z₀ 混合圈链图传播子的构架方式及其重整化问题作了详细分析与讨论, 并完成了有关解析计算, 获得了由参与电弱相互作用的各种混合圈构成的γ和Z₀的重整化链图传播子的解析计算结果. 此外, 我们还将此结果应用于高能物理中备受关注的一类轻子反应e⁺e^-→μ⁺μ^-中, 获得了在γ和Z₀所构架出的重整化混合圈链图传播中e⁺e^-→μ⁺μ^-反应截面的解析计算结果, 并将本文所获得的这一理论计算结果与实验观测值作了对比分析, 发现本文理论计算结果与实验观测值符合非常好, 并由此也获得了有关辐射修正的重要信息. 本文研究结果也可为探讨一般复杂传播子的理论研究与应用提供某些参考. 关键词： 标准模型 链图传播子 重整化 辐射修正     

Bhabha散射中的完整电弱效应与标准模型的完美性问题

本文在电弱统一标准模型(SM)的理论框架中, 对Bhabha散射问题作了全新的理论分析与深入研究.在具体研究方法上采用了量子场论微扰理论中的一种全新计算模式——重整化链图传播子理论, 并应用到Bhabha散射的计算研究中. 在SM中, 本文需要考虑Bhabha散射内部过程的完整电弱作用效应, 为此应寻求出由光子gamma 和中间玻色子Z_0构成的复杂混合圈链图重整化传播子, 然后利用这类传播子计算出Bhabha散射中由混合圈链图传播子传递完整电弱作用下的反应截面. 这一理论计算结果与实验值在实验观测误差范围内吻合较好. 本文这一重要研究结果不但从另一个侧面证实了SM理论描述电弱作用下的粒子反应的精确性; 而且也暗示SM理论应该是一个十分完美的理论, 理论终极预言的且被学术界长期特别关注的希格斯“神秘粒子”最终被寻找到的可能性应该是十分大的.     

Bhabha散射中的完整电弱效应与标准模型的完美性问题

本文在电弱统一标准模型(SM)的理论框架中,对Bhabha散射问题作了全新的理论分析与深入研究.在具体研究方法上采用了量子场论微扰理论中的一种全新计算模式——重整化链图传播子理论,并应用到Bhabha散射的计算研究中.在SM中,本文需要考虑Bhabha散射内部过程的完整电弱作用效应,为此应寻求出由光子γ和中间玻色子Z0构成的复杂混合圈链图重整化传播子,然后利用这类传播子计算出Bhabha散射中由混合圈链图传播子传递完整电弱作用下的反应截面.这一理论计算结果与实验值在实验观测误差范围内吻合较好.本文这一重要研究结果不但从另一个侧面证实了SM理论描述电弱作用下的粒子反应的精确性;而且也暗示SM理论应该是一个十分完美的理论,理论终极预言的且被学术界长期特别关注的希格斯"神秘粒子"最终被寻找到的可能性应该是十分大的.     

一维体系的电声子相互作用和声子激发

通过一维金属卤素络合物模型和一维分子晶体模型研究了一维体系的电声子相互作用和声子激发．给出了在绝热近似下重整化的声子色散关系．结果表明：（１）两个模型中电声子相互作用不同，导致前者声频声子重整化可略而后者重整化修正明显；（２）与高分子材料的Ｓｕ-Ｓｃｈｒｉｅｆｅｒ-Ｈｅｅｇｅｒ模型不同，两个模型的声子谱均无能隙 关键词：     

一种胶子分布函数的动力学模型

本文利用分布函数的动力学模型, 改进了Buras和Gaemers关于胶子分布函数的参数化工作^[4], 得到了一个能较好地满足QCD演化方程(LLA近似)的胶子分布函数的简单参数式. 在这基础上分析了核子中胶子成份的性质, 指出胶子分布函数可以看作由软、硬两个不同部分所组成的.     

Infrared behavior and fixed points in Landau-gauge QCD

We investigate the infrared behavior of gluon and ghost propagators in Landau-gauge QCD by means of an exact renormalization group equation. We explain how, in general, the infrared momentum structure of Green functions can be extracted within this approach. An optimization procedure is devised to remove residual regulator dependences. In Landau-gauge QCD this framework is used to determine the infrared leading terms of the propagators. The results support the Kugo-Ojima confinement scenario. Possible extensions are discussed.     

Kugo-Ojima confinement and QCD Green''s functions in covariant gauges

In Landau gauge QCD the Kugo-Ojima confinement criterion and its relations to the infrared behaviour of the gluon and ghost propagators are reviewed. It is demonstrated that the realization of this confinement criterion (which is closely related to the Gribov-Zwanziger horizon condition) results from quite general properties of the ghost Dyson-Schwinger equation. The numerical solutions for the gluon and ghost propagators obtained from a truncated set of Dyson-Schwinger equations provide an explicit example for the anticipated infrared behaviour. The results are in good agreement, also quantitatively, with corresponding lattice data obtained recently. The resulting running coupling approaches a fixed point in the infrared, (0) = 8.915/N_c. Solutions for the coupled system of Dyson-Schwinger equations for the quark, gluon and ghost propagators are presented. Dynamical generation of quark masses and thus spontaneous breaking of chiral symmetry takes place. In the quenched approximation the quark propagator functions agree well with those of corresponding lattice calculations. For a small number of light flavours the quark, gluon and ghost propagators deviate only slightly from the ones in quenched approximation. While the positivity violation of the gluon spectral function is manifest in the gluon propagator, there are no clear indications of analogous positivity violations for quarks so far.     

On the infrared behavior of Landau gauge Yang–Mills theory

We discuss the properties of ghost and gluon propagators in the deep infrared momentum region of Landau gauge Yang–Mills theory. Within the framework of Dyson–Schwinger equations and the functional renormalization group we demonstrate that it is only a matter of infrared boundary conditions whether infrared scaling or decoupling occurs. We argue that the second possibility is at odds with global BRST symmetry in the confining phase. For this purpose we improve upon existing truncation schemes in particular with respect to transversality and renormalization.     

Combining infrared and low-temperature asymptotes in Yang-Mills theories

We demonstrate that the powerlike nonperturbative behavior of gluon and ghost propagators in the infrared limit of Yang-Mills theories can provide at finite temperatures T a negative T4 contribution to the pressure and energy density. The existence of a mass gap then implies new relations between the infrared critical exponents of gluon and ghost propagators.     

Temperature dependence of gluon and ghost propagators in Landau-gauge Yang-Mills theory below the phase transition

The Dyson-Schwinger equations of Landau-gauge Yang-Mills theory for the gluon and ghost propagators are investigated. Numerical results are obtained within a truncation scheme which has proven to be successful at vanishing temperature. For temperatures up to 250 MeV we find only minor quantitative changes in the infrared behavior of the gluon and ghost propagators. The effective action calculated from these propagators is temperature independent within the numerical uncertainty.Received: 25 August 2004, Revised: 29 March 2005, Published online: 8 June 2005PACS: 11.10.Wx, 12.38.Aw, 14.70.Dj     

Verifying the Kugo-Ojima confinement criterion in Landau gauge Yang-Mills theory

Expanding the Landau gauge gluon and ghost two-point functions in a power series we investigate their infrared behavior. The corresponding powers are constrained through the ghost Dyson-Schwinger equation by exploiting multiplicative renormalizability. Without recourse to any specific truncation we demonstrate that the infrared powers of the gluon and ghost propagators are uniquely related to each other. Constraints for these powers are derived, and the resulting infrared enhancement of the ghost propagator signals that the Kugo-Ojima confinement criterion is fulfilled in Landau gauge Yang-Mills theory.     

Infrared exponents and the running coupling of Landau gauge QCD and their relation to confinement

The infrared behaviour of the gluon and ghost propagators in Landau gauge QCD is reviewed. The Kugo-Ojima confinement criterion and the Gribov-Zwanziger horizon condition result from quite general properties of the ghost Dyson-Schwinger equation. The numerical solutions for the gluon and ghost propagators obtained from a truncated set of Dyson-Schwinger equations provide an explicit example for the anticipated infrared behaviour. The results are in good agreement with corresponding lattice data obtained recently. The resulting running-coupling approaches a fix point in the infrared, . Two different fits for the scale dependence of the running coupling are given and discussed.Received: 30 September 2002, Published online: 22 October 2003PACS: 12.38.Aw General properties of QCD (dynamics, confinement, etc.) - 14.70.Dj Gluons - 12.38.Lg Other nonperturbative calculations - 11.15.Tk Other nonperturbative techniques - 02.30.Rz Integral equations     

Infrared gluon and ghost propagators from lattice QCD

We report on the infrared limit of the quenched lattice Landau gauge gluon and ghost propagators as well as the strong-coupling constant computed from large asymmetric lattices. The infrared lattice propagators are compared with the pure power law solutions from Dyson-Schwinger equations (DSE). For the gluon propagator, the lattice data is compatible with the DSE solution. The preferred measured gluon exponent being ∼0.52, favouring a vanishing propagator at zero momentum. The lattice ghost propagator shows finite-volume effects and, for the volumes considered, the propagator does not follow a pure power law. Furthermore, the strong-coupling constant is computed and its infrared behaviour investigated.     

Infrared gluon and ghost propagator exponents from lattice QCD

The compatibility of the pure power law infrared solution of QCD and lattice data for the gluon and ghost propagators in Landau gauge is discussed. For the gluon propagator, the lattice data are well described by a pure power law with an infrared exponent κ∼0.53, in the Dyson–Schwinger notation. κ is measured using a technique that suppresses finite volume effects. This value is consistent with a vanishing zero momentum gluon propagator, in agreement with the Gribov–Zwanziger confinement scenario. For the ghost propagator, the lattice data seem not to follow a pure power law, at least for the range of momenta accessed in our simulation.     

Two-Loop Improved Truncation of the Ghost-Gluon Dyson-Schwinger Equations: Multiplicatively Renormalizable Propagators and Nonperturbative Running Coupling

The coupled Dyson-Schwinger equations for the gluon and ghost propagators are investigated in the Landau gauge using a two-loop improved truncation that preserves the multiplicative renormalizability of the propagators. In this truncation all diagrams contribute to the leading-order infrared analysis. The infrared contributions of the nonperturbative two-loop diagrams to the gluon vacuum polarization are computed analytically, and this reveals that infrared power-behaved propagator solutions only exist when the squint-diagram contribution is taken into account. For small momenta the gluon and ghost dressing functions behave like (p ²)² and (p ²)^–, respectively, and the running coupling exhibits a fixed point. The values of the infrared exponent and fixed point depend on the precise details of the truncation. The coupled ghost-gluon system is solved numerically for all momenta, and the solutions have infrared behaviors consistent with the predictions of the infrared analysis. For truncation parameters chosen such that = 0.5, the two-loop improved truncation is able to produce solutions for the propagators and running coupling which are in very good agreement with recent lattice simulations.Received March 17, 2003; accepted May 9, 2003 Published online September 24, 2003