Gluon Propagator and Heavy Quark Potential in an Anisotropic QCD Plasma

The hard-loop resummed propagator in an anisotropic QCD plasma in general linear gauges are computed. We get the explicit expressions of the gluon propagator in covariant gauge, Coulomb gauge and temporal axial gauge. Considering one gluon exchange, the potential between heavy quarks is defined through the Fourier transform of the static propagator. We find that the potential exhibits angular dependence and that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment.     

幂级数展开法计算周期阻尼振子路径积分短时传播子

文章用Schwinger方法与Makri等人发展的幂级数展开法研究了周期阻尼简谐振子的传播子.研究表明,这两种方法所获得的短时传播子非常接近,但是后者比前者要简单得多,这给研究复杂系统的传播子提供了一个简单可靠的方法.     

All the fundamental massless fields in bosonic string theory

A systematic analysis of the massless fields in the mass spectra of bosonic strings is carried in arbitrary spacetime dimension D > 2. The emphasis is put on the derivations of their propagators, their polarization aspects and the underlying constraints involved. The treatment is given, in the presence of external sources, in the celebrated Coulomb gauge for the second rank tensors and vector fields, which ensures positivity – a result which is also established in the process. No constraints are imposed on the external sources so that their components may be varied independently generating complete expressions for the propagators. This latter condition is an important one in the generation of dynamical theories with constraints involving such modifications as Faddeev‐Popov factors.     

Quantum effects of nonlinear spin waves in ferromagnets

We investigate a squeezed thermal spin state of nonlinear spin waves in Heisenberg ferromagnets. In this state, the magnon system possesses a new kind of quasiparticle, the dressed magnon, whose mass is a monotonically decreasing function of temperature. The noise of one spin component in the squeezed thermal spin state can be below the noise level in the vacuum state. The magnon system undergoes a first-order phase transition from the normal state to the squeezed thermal spin state. The critical temperature is much lower than the Curie temperature. A possible detection scheme based on a polarized neutron-scattering technique is suggested.     

Possible DNA damage by oxidation products of guanine: A density functional and electron propagator theoretical study

The stability and reactivity of seven guanine oxidation products (GOP), which contain 8‐oxo‐7,8‐dihydroguanine (8‐oxoG) have been studied and compared with the four nucleobases, such as adenine, cytosine, guanine, and thymine. It has been possible with the use of density functional theory and electron propagator theory (EPT), to evaluate their relation with certain ionization induced process, which produce damage to DNA. Using the application of Koopmans's theorem, EPT provides alternatively a reliable way to calculate the vertical ionization potential (VIP) and vertical electron affinity (VEA). This process has been used to obtain other reactivity indexes, such as: electronegativity and hardness. In the nucleobases and the GOP studies, we observed the following: guanine and 8‐oxo‐7,8‐dihydroguanine were the lowest VIP, and 8‐oxoG was the lowest hardness. This let us confirm that these species are the most susceptible to change their electron densities and transform in other GOP. Particularly, the GOP, Sp(R), Sp(S), and Z were the highest VIP. It allows us to say that they are the most stable. Z and Iz were the highest VEA; this suggests that they have a big capacity to accept electrons and form anionic centers in DNA. The GOP, which was considered in this study, showed hardness values between 9.1 and 10.4 because of π‐conjugation; therefore, these GOP could be good candidates to participate in DNA transversions. © 2012 Wiley Periodicals, Inc.     

On analytic formulas of Feynman propagators in position space

We correct an inaccurate result of previous work on the Feynman propagator in position space of a free Dirac field in(3+1)-dimensional spacetime; we derive the generalized analytic formulas of both the scalar Feynman propagator and the spinor Feynman propagator in position space in arbitrary(D+1)-dimensional spacetime; and we further find a recurrence relation among the spinor Feynman propagator in(D+l)-dimensional spacetime and the scalar Feynman propagators in(D+1)-,(D-1)-and(D+3)-dimensional spacetimes.     

Real-Time Thermal Schwinger-Dyson Equation for Quark Self-energy in Landau Gauge

By means of a formal expression of Cornwall-Jackiw-Tomboulis effective potential for quark propagator at finite temperatures and finite quark chemical potentials, we derive the real-time thermal Schwinger-Dyson equation for quark propagator in Landau gauge. Denote the inverse quark propagator by A（p^2）ψ - B（p^2）, we argue that, when temperature T is lower than the given infrared momentum cutoff pc, A（p^2） = 1 is a feasible approximation and can be assumed in discussions of chiral symmetry phase transition problem in QCD.     

自旋1/2铁磁模型的相互作用淬火

本文设想了一个相互作用淬火后在 时刻开启的海森堡反铁磁模型,并对其进行了解析分析.在低温近似下,通过求解海森堡方程给出该系统随时间演化的自旋算符的解析形式.主要推算并讨论了自旋传播子,通过对传播子的讨论发现这个新体系的自旋波谱发生了变化.文末对此现象进行了讨论.     

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.