Gluon condensate from superconvergent QCD sum rule

Sum rules for the nonperturbative piece of correlators (specifically, the vector current correlator) are discussed. The sum rule subtracting the perturbative part is of the superconvergent type. Thus it is dominated by the bound states and the low-energy production cross section. It leads to a determination of the gluon condensate _sG². We find _sG²0.048±0.030 GeV⁴.     

Nonperturbative dynamics in the color-magnetic QCD vacuum

In the deconfinement phase of QCD, quarks and gluons interact with the dense stochastic color-magnetic vacuum. We consider the dynamics of quarks in this deconfinement phase using the field correlators method and derive an effective nonperturbative interquark potential, in addition to the usual perturbative short-range interaction. We find the resulting angular-momentum-dependent interaction to be attractive enough to maintain bound states and, for light quarks (and gluons), to cause emission of quark and gluon pairs. Possible consequences for the strong-interacting quark-gluon plasma are briefly discussed. The text was submitted by the authors in English.     

Bremsstrahlung from colour charges as a source of soft particle production in hadronic collisions

It is proposed that soft particle production in hadronic collisions is dominated by multiple gluon exchanges between partons from the colliding hadrons, followed by radiation of hadronic clusters from the coloured partons distributed uniformly in rapidity. This explains naturally two dominant features of the data: (a) the linear increase of rapidity spectra in the regions of limiting fragmentation and, (b) the proportionality between the increasing width of the limiting fragmentation region and the height of the central plateau.     

Gluon condensate in color superconductivity

In color superconductor the gluon condensate drops down at moderate density but goes up at high density and can even exceed its vacuum value when the density is high enough.     

Gluon condensate in color superconductivity

In color superconductor the gluon condensate drops down at moderate density but goes up at high density and can even exceed its vacuum value when the density is high enough.     

Nonperturbative dynamics in the chromomagnetic QCD vacuum above the deconfinement temperature

We investigate the residual chromomagnetic nonperturbative interaction between colour sources which survives above the deconfinement temperature. This interaction is demonstrated to be attractive enough to support bound states of quarks (and gluons). Although, for heavy quarks, such bound states appear to be very shallow and thus to dissociate easily, for light quarks (and gluons), the interaction is found to be strong enough to lead to quark (gluon) pair creation in the vacuum and thus to a complete rebuild of the vacuum state. The text was submitted by the authors in English.     

p-wave superconductivity

Spin triplet, p-wave superfluidity was discovered in ³He a quarter of a century ago, and unconventional spin singlet d-wave superconductivity is now known to exist in the high-temperature superconducting cuprates. An established example of a spin triplet superconductor has still, however, been lacking. In the past few years, evidence suggesting the existence of triplet pairing has been reported in several correlated electron compounds, with perhaps the most consistent picture emerging in the layered perovskite oxide Sr₂RuO₄. A brief review is given of the recent developments, stressing the important role played by high-quality samples with long mean free paths.     

Applying colour science in colour design

Although colour science has been widely used in a variety of industries over the years, it has not been fully explored in the field of product design. This paper will initially introduce the three main application fields of colour science: colour specification, colour-difference evaluation and colour appearance modelling. By integrating these advanced colour technologies together with modern colour imaging devices such as display, camera, scanner and printer, some computer systems have been recently developed to assist designers for designing colour palettes through colour selection by means of a number of widely used colour order systems, for creating harmonised colour schemes via a categorical colour system, for generating emotion colours using various colour emotional scales and for facilitating colour naming via a colour-name library. All systems are also capable of providing accurate colour representation on displays and output to different imaging devices such as printers.     

Longitudinal viscous hydrodynamic evolution for the shattered colour glass condensate

We investigate hydrodynamic evolution of the quark-gluon plasma for the colour glass condensate type initial conditions. We solve full second-order viscous hydrodynamic equations in the longitudinal direction to find that non-boost invariant expansion leads to visible deformation on the initial rapidity distribution. The results indicate that hydrodynamic evolution with entropy production from viscosity plays an important role in determining parameters for the initial distributions.     

Practical colour management

Spectrophotometers have been successfully used for colour measurement. This paper addresses digital imaging as a complementary and alternative method of colour measurement and appearance and an effective communication tool as part of a practical colour management programme within the supply chain of a textile retailer. The specific needs—to measure and communicate textured dyed material and printed fabric—are discussed, as well as the colour specification and quality control (QC) of currently un-measurable fabrics and accessories. A unique method of using digital imaging for the assessment of colour fastness will also be discussed.     

Asymptotics of QCD traveling waves with fluctuations and running coupling effects

Extending the Balitsky–Kovchegov (BK) equation independently to running coupling or to fluctuation effects due to pomeron loops is known to lead in both cases to qualitative changes of the traveling-wave asymptotic solutions. In this paper we study the extension of the forward BK equation, including both running coupling and fluctuations effects, extending the method developed for the fixed coupling case [E. Brunet, B. Derrida, A.H. Mueller, S. Munier, Phys. Rev. E 73 (2006) 056126, cond-mat/0512021]. We derive the exact asymptotic behavior in rapidity of the probabilistic distribution of the saturation scale.     

Gravitoelectric-electric coupling via superconductivity

Recently we demonstrated theoretically that the carriers of quantized angular momentum in superconductors are not the Cooper pairs but the lattice ions, which must execute coherent localized motion consistent with the phenomenon of superconductivity. We demonstrate here that in the presence of an external magnetic field, the free superelectron and bound ion currents largely cancel providing a self-consistent microscopic and macroscopic interpretation of near-zero magnetic permeability inside superconductors. The neutral mass currents, however, do not cancel, because of the monopolar gravitational charge. It is shown that the coherent alignment of lattice ion spins will generate a detectable gravitomagnetic field, and in the presence of a time-dependent applied magnetic vector potential field, a detectable gravitoelectric field.     

Structure and superconductivity in the ternary silicide CaAlSi

Using the linear response-linearized Muffin-tin orbital (LR-LMTO) method, we study the electronic band structure, phonon spectra, electron-phonon coupling and superconductivity for c-axis ferromagnetic-like (F-like) and antiferromagnetic-like (AF-like) structures in ternary silicide CaAlSi. The following conclusions are drawn from our calculations. If Al and Si atoms are assumed to arrange along the c axis in an F-like long-range ordering (-Al-Al-Al-and-Si-Si-Si-), one could obtain the ultrasoft B_1g phonon mode and thus very strong electron-phonon coupling in CaAlSi. However, the appearance of imaginary frequency phonon modes indicates the instability of such a structure. For Al and Si atoms arranging along the c axis in an AF-like long-range ordering (-Al-Si-Al-), the calculated electron-phonon coupling constant is equal to 0.8 and the logarithmically averaged frequency is 146.8 K. This calculated result can correctly yield the superconducting transition temperature of CaAlSi by the standard BCS theory in the moderate electron-phonon coupling strength. We propose that an AF-like superlattice model for Al (or Si) atoms along the c direction may mediate the inconsistency estimated from theory and experiment, and explain the anomalous superconductivity in CaAlSi.      

Unconventional superconductivity

‘Conventional’ superconductivity, as used in this review, refers to electron–phonon-coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon exchange but instead by exchange of some other kind, e.g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu₂Si₂, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6?K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw T_c jump to 164?K by 1994. Further progress in high-temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materials – from 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples – with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial – e.g. FeSe on SrTiO₃, and H₂S under high pressure) are briefly covered, even though their ‘conventionality’ is not yet fully determined.     

QCD求和规则与强子物理

量子色动力学（QCD）求和规则是强子物理研究中的一种重要的非微扰方法, 已经成为强子物理与核物理研究中有力的工具。 简单介绍了QCD求和规则的基本概念、 方法与应用, 特别讨论了QCD求和规则近年来的发展和与之相关的一些前沿问题。 QCD sum rule is an important nonperturbative method in hadron physics, it has been a powerful technique in study of hadron physics and nuclear physics.We give a brief introduction to the basic idea, the method and its application of QCD sum rule, emphasize the development of this method and some topics in recent years.     

Heavy fermion superconductivity

The quest for a precise identification of the symmetry of the order parameter in heavy fermion systems has really started with the discovery of the complex superconducting phase diagram in UPt₃. About 10 years latter, despite numerous experiments and theoretical efforts, this is still not achieved, and we will quickly review the present status of knowledge and the main open question. Actually, the more forsaken issue of the nature of the pairing mechanism has been recently tackled by different groups with macroscopic or microscopic measurement, and significant progress have been obtained. We will discuss the results emerging from these recent studies which all support non-phonon-mediated mechanisms.     

高压下过渡金属二硫属化物的超导电性

过渡金属二硫属化物是一类典型的二维类石墨烯层状结构的材料,相比于石墨烯的全碳元素组成以及无带隙的电子结构特点,具有更丰富的元素组成、多样的微观结构和奇异的物理性质。过渡金属二硫属化物强烈的各向异性以及在催化、光伏器件和储能材料等领域的优异表现,引起了科学家们浓厚的研究兴趣。它们的层间范德瓦耳斯间隙、层间范德瓦耳斯相互作用、层间堆垛次序对压力非常敏感,易于通过压力调控其晶体结构和电子能带结构,进而发生电子基态的变化。过渡金属二硫属化物的电子基态可以是莫特绝缘体、激子绝缘体、电荷密度波、半导体、(拓扑)半金属、金属,甚至是超导体。在常压条件下,部分过渡金属二硫属化物具有超导电性。实验表明,压力可以诱导过渡金属二硫属化物非超导母体发生超导转变,或者提高超导母体的超导转变温度。文章以典型的过渡金属二硫属化物为例,概述了其在高压调控下超导电性的响应,并简要讨论产生超导电性的物理机制。     

Then and now: James Clerk Maxwell and colour

A survey of the researches of James Clerk Maxwell into the production and perception of colour is presented, and links to a selection of present day applications of colour science are indicated. Although false colour photography was not known in Maxwell's time, aspects of his work, suitably interpreted, have a bearing on the wide applicability of the technique. An outline is given of one application of false colour to visualising and analysing data on fluid motion.