CONFINEMENT PROPERTIES OF THE PURE GAUGE FIELDS ON COSET SPACE OF AN ABELIAN CHIRAL GROUP

In this paper the lattice current-current propagator is calculated and the influence of coset pure gauge fields of an Abelian chiral group G=U₁×U⁵ on confinement properties of a quark system is discussed by virtue of the Wilson's criterion of lattice gauge theory. When subgroup H is U₁, the coset pure gauge fields only contribute a perimeter law factor to the current-current propagator which has no influence on confinement properties of the system. When subgroup H is U⁵, the coset pure gauge fields also have no influence on confinement properties of the system.     

LATTICE FORMULATION OF THE PURE GAUGE FIELDS ON COSET SPACE

In this paper we construct a lattice formulation of the pure gauge fields on a coset space in the cases of a group G with non-trivial topological property and of a chiral group G, and present a local gauge invariant action of a quark system on a four-dimensional Euclidean space lattice, which has the continuum limit as usual. For non-chiral group with trivial topological property, it is shown that the coset pure gauge fields have no influence on the confinement properties of the confinement properties of the quark system by calculating lattice current-current propagator when the coset pure gauge fields remain manifest.     

CONFINEMENT PROPERTIES OF PURE GAUGE FIELCS ON COSET SPACE OF THE NON-ABELIAN CHIRAL GROUP

In this paper the method of lattlce gauge theories is applied to the investigation of the effect of coset pure gauge fields of the non-Abelian chiral group on the confinement properties of a system. In particular, the current-current propagator of the coset G/H=SU(2)_L×(2)_r/SU(2) model is calculated. Then it IS found that the pure gauge fields-on coset space only offer a perimeter law factor which does not change the confinement properties of a physical system.     

LATTICE FORMULATION OF THE PURE GAUGE FIELDS ON COSET SPACE

In this paper we construct the lattice formulation of the pure gauge fields in a coset space in the cases of a group G with non-trivial topological property and of a chiral group G, and present a local gauge invariant action of a quark system on a fourdimensional Euclidean space lattice, which has the continuum limit as usual. For non-chiral group with trivial topological property, it is shown that the coset pure gauge fields have no influence on the confinement properties of the quark system by calculating latt-ice current-current propagztor when the coset pure gauge fields are retained manifest1y.     

Center flux correlation in SU(2) Yang-Mills theory

By using the method of center projection, the center vortex part of the gauge field is isolated and its propagator is evaluated in the center Landau gauge, which minimizes the open 3-dimensional Dirac volumes of nontrivial center links bounded by the closed 2-dimensional center vortex surfaces. The center field propagator is found to dominate the gluon propagator (in the Landau gauge) in the low momentum regime and to give rise to a power-law correction proportional to p(-2.9(1)) at high momentum. The screening mass of the center vortex field vanishes above the critical temperature of the deconfinement phase transition, which naturally explains the second order nature of this transition consistent with the vortex picture. Finally, the ghost propagator of the maximal center gauge is found to be infrared finite and, thus, shows that the coset fields play no role for confinement.     

Evidences of dense Kondo behaviour in the U-Au system: Electrical and magnetic investigations in U14Au51 and UAu2

U₁₄Au₅₁ and UAu₂ were recently demonstrated the two correct phases stable at room temperature in the U-Au system. Magnetic susceptibility (1.5–300 K) and electrical resistivity (10–800 K) measurements were performed in samples of both phases. Magnetic susceptibility temperature behaviour gives evidences of an antiferromagnetic transition at 23 K in U₁₄Au₅₁, whereas no magnetic order is detected in UAu₂. In both compounds, Kondo-like logarithmic behaviour in electrical resistivity temperature trend is found. Effects already observed in U₂Zn₁₇ and UAl₂ are respectively found in U₁₄Au₅₁ and UAu₂. Possible “heavy fermion” properties of these compounds 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.     

Magnetic and transport properties of some U3T3X4-compounds (T = Co, Ni, Cu and X = Sb, Sn)

We have prepared and studied a new series of isostructural U₃T₃X₄-compounds with T = Co, Ni, Cu for X = Sb and T = Ni for X = Sn. Ferromagnetism is found for U₃Co₃Sb₄ and U₃Cu₃Sb₄ below 10 and 88 K, respectively. In contrast, no magnetic order was observed down to 1.7 K for the semiconductor U₃Ni₃Sb₄ and the “moderately” heavy-fermion system U₃Ni₃Sb₄.     

Calculating the Cabibbo angle

Within a gauge theory based on the gauge group SU₂ × SU₂ × U₁ and on the four quark flavours u, d, s, and c the Cabibbo angle is calculated in terms of the quark mass ratios. The u and d quark masses are zero in the absence of weak interaction mixing due to the existence of a discrete symmetry R. The calculated value of the Cabibbo angle is in agreement with the observed value.     

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.     

Exceptional coset spaces and unification in six dimensions

The coset spaces E₈/SO(10)×H_F allow complex structures which can account for three quark–lepton generations including right-handed neutrinos. We show that in the context of supersymmetric SO(10) gauge theories in 6 dimensions they also provide the Higgs fields which are needed to break the electroweak and B−L gauge symmetries, and to generate small neutrino masses via the seesaw mechanism.     

Accessing directly the properties of fundamental scalars in the confinement and Higgs phase

The properties of elementary particles are encoded in their respective propagators and interaction vertices. For a SU(2) gauge theory coupled to a doublet of fundamental complex scalars these propagators are determined in both the Higgs phase and the confinement phase and compared to the Yang–Mills case, using lattice gauge theory. Since the propagators are gauge dependent, this is done in the Landau limit of the ’t Hooft gauge, permitting to also determine the ghost propagator. It is found that neither the gauge boson nor the scalar differ qualitatively in the different cases. In particular, the gauge boson acquires a screening mass, and the scalar’s screening mass is larger than the renormalized mass. Only the ghost propagator shows a significant change. Furthermore, indications are found that the consequences of the residual non-perturbative gauge freedom due to Gribov copies could be different in the confinement and the Higgs phase.     

热阴极电离真空计的线性理论

从繁流放电理论可直接导出热阴极电离真空计的特性方程,证明通常的概念即在热计的电子流i_e一定时其离子流i₊与压强P成正比的关系,只在离子流甚小于电子流时才能成立。在被测气体的压强较高时,离子流和压强之间呈现下列指数关系: i₊/i_e=1-e^{(-(K₁P-K₂P2))}(K₁及K₂为常数),且随着压强的增长而逐步趋于饱和。进一步的推导则得出,当容许测量误差为1％时,热计的线性上限(临界压强)为P_c=0.22/Г,此处Г为热计的灵敏度。这种理论可以容易地解释近年来一些实验工作者例如Nottingham,Schultz,Goto,Hinzpeter等的实验结果。此外我们还使用了特殊设计的“封闭式”电离计作实验,得到的结果和理论预计十分符合。这种电离计本身则可用作10^-7～0.6托的宽程量具。 关键词：     

Energy excitations in three-axial magnets with single-ion and exchange anisotropies

The energy spectra of three-axial ferromagnets like U₃P₄ and ferrimagnets like U₃Sb₄ are presented and their properties are discussed. In case of U₃Sb₄ we find an interesting example of a magnetic structure which, due to the single-ion anisotropy, is unstable in the spin wave approximation. The k² dependence of magnon energies requires re-examination of the temperature dependence of the magnetisation and of the specific heat.     

Quark confinement physics from quantum chromodynamics

We show the construction of the dual superconducting theory for the confinement mechanism from QCD in the maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. We find that essence of infrared abelian dominance is naturally understood with the off-diagonal gluon mass m_off ≈- 1.2GeV induced by the MA gauge fixing. In the MA gauge, the off-diagonal gluon amplitude is forced to be small, and the off-diagonal gluon phase tends to be random. As the mathematical origin of abelian dominance for confinement, we demonstrate that the strong randomness of the off-diagonal gluon phase leads to abelian dominance for the string tension. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system. We investigate the monopole-current system in the MA gauge by analyzing the dual gluon field B_μ. We evaluate the dual gluon mas as m_B = 0.4 0.5GeV in the infrared region, which is the lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Owing to infrared abelian dominance and infrared monopole condensation, QCD in the MA gauge is describable with the dual Ginzburg-Landau theory.     

Monopoles, vortices and confinement in SU(3) gauge theory

We compute, in SU(3) pure gauge theory, the vacuum expectation value (VEV) of the operator which creates a Z₃ vortex wrapping the lattice through periodic boundary conditions (dual Polyakov line). The technique used is the same already tested in the SU(2) case. The dual Polyakov line proves to be a good disorder parameter for confinement, and has a similar behaviour to the monopole condensate. The new features which characterise the construction of the disorder operator in SU(3) are emphasised.     

水下翼型结构流噪声实验研究

为测量流激水下翼型结构的流噪声,提出了一种混响箱测量方法。在重力式水洞中搭建了一套实验测量系统,利用混响箱法测量了水下翼型结构模型的辐射声功率。在此基础上研究了流速及结构参数(厚度、肋、声学覆盖层)对其辐射声功率的影响。结果表明:当流速小于5 m/s时,辐射声功率随流速的6次方增长,符合偶极子的辐射规律;当流速大于5 m/s时,辐射声功率随流速的10土1次方规律增长,不再按偶极子的规律辐射;若对水下翼型结构模型加厚、加环肋及外部敷设黏弹性材料,均可在一定程度上抑制流噪声。此研究方法可对水下复杂结构的辐射声功率测量及结构优化设计提供一定的参考。      

Nonequilibrium Green's Function Approach to Resonant Magnetotunneling Through a Quantum Dot

Keldysh's nonequilibrium Green's function is applied to studying resonant magnetotunneling through a quantum dot. We propose a microscopic Anderson-impurity-like Hamiltonian in which two kinds of the on-site Coulomb interactions are introduced:the interaction of two electrons at the same Landau level with different spins, U₁ and the interaction for the electrons between different Landau levels, U₁. I-V curves are obtained under different magnetic fields in asymmetrical structures which can display both the energy quantization and singleelectron charging effect. The theoretical results are in good agreement with the experiments qualitatively. The linear-response conductance is also discussed.     

Heavy Meson Decay Constants to 1/mQ

We introduce the vector meson contributions in heavy-light chiral perturbation theory (HLCPT) and construct the Lagrangian and current. to the order 1/m_Q. With this, to the order 1/∧_csb²(∧_csb is the chiral symmetry breaking scale) we calculate corrections to f_D and f_B arising from coupled-channel effects to the orders 1/m_C, and 1/m_b. At the tree level in HLCPT, using the relativistic Bethe-Salpeter (BS) equation with the kernel containing a confinement term and a gluon exchange term in a covarian t generalization of the coulomb gauge we calculate f_D⁽⁰⁾ and f_B⁽⁰⁾ when m_Q→∞ as well as the 1/m_Q corrections. HLCPT and the heavy quark effective theory (HQET) are matched at the scale ACsb. Adding the perturbative and nonperturbative contributions we give the values for f_D and f_B, respectively. It is found that our result is in agreement with the relation f_D = f_B fiom lattice calculations.     

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.