The screening of colour charge in the numerical hopping-parameter expansion

The screening of the quark-antiquark potential by dynamical quark-antiquark pairs is numerically investigated in SU(2) colour gauge theory with Wilson fermions. The expected qualitative behaviour is born out by a high-order hopping-parameter expansion. The screening length is about 0.8 fm and the dissociation energy of a heavy quark-antiquark pair is near 600–800 MeV.     

Time Evolution of Colour Screening and Suppression of J/ψ、χ and ψ' by Quark-Gluon Plasma

We discuss the time evolution of the colour screening and J/ψ、χ and ψ' suppression by the quark-gluon plasma within the non-relativistic confining potential model.     

Strong coupling 1/N c expansion in the gluonic sector of lattice QCD: The next order

Continuing our previous work we determined the gluonic vacuum state up to sixth order and the lowest states with external quark-antiquark and (unscreened) gluon-gluon sources up to fourth order in the strong coupling 1/N _c expansion on the lattice. Unlike previously, we used here the colour electric flux operators on the links to define the colour electric energy. Additional remarks concerning the screening of external gluon sources and the analytic continuation toN _c =3 and zero lattice spacing are also included.     

A Unified Description of Baryon Spectrum in a Screened Potential Model

A potential model with screened confinement is proposed to calculate baryon spectrum. The results show that with the consideration of the colour screening effect, the theoretical predictions for both positive and negative N and Δ systems can be improved simultaneously. Moreover, by utilizing the potential, the calculated spectra for strange baryons (contain s quark), such as ∧∑ and Ω, can fit the experimental data better.     

Kaonic Nuclear Cluster Kpp in Quark Delocalization Colour Screening Model

The quark-delocalization colour-screening model is employed to study the kaonic nuclear cluster K-pp system. The calculation shows that there is a strong effective attraction between kaon and protons. The bound state can be formed and the binding energy is estimated to be about 80 MeV, and the space configuration is a symmetrical linear triatomic molecule with radius 1.15 fm. The results also show that the quark delocalization is responsible for the strong attraction in the system and the colour screening adds a little attraction in this case.     

Quarkonium suppression: Gluonic dissociation vs. colour screening

We evaluate the suppressionof J/ψ production in an equilibrating quark gluon plasma for two competing mechanisms: Debye screening of colour interaction and dissociation due to energetic gluons. Results are obtained for S + S and Au + Au collisions at RHIC and LHC energies. At RHIC energies the gluonic dissociation of the charmonium is found to be equally important for both the systems while the screening of the interaction plays a significant role only for the larger systems. At LHC energies the Debye mechanism is found to dominate both the systems. While considering the suppression of directly produced T at LHC energies, we find that only the gluonic dissociation mechanism comes into play for the initial conditions taken from the self screened parton cascade model in these studies.     

Generalized heat kernel coefficients

In hadronic collisions, the mini-jet cross section is formally divergent in the limit . We argue that this divergence is tamed by some effective colour correlation length scale of the hadron. A toy model of the hadronic structure is introduced, that allows an estimate of the screening effects, and especially their energy dependence.     

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.     

Colour naming

An experimental study exploring colour ranges corresponding to different colour names has been conducted. Available colour terms in Turkish language have been identified and the most frequently known or used colour terms have been attained. Using the Munsell Color System, colour ranges reflecting the colour naming and colour perception of Turkish people, have been constructed for each colour term. The discussion of the findings and observations during the research are also included.     

On a predictive scheme for colour image quantization

In this paper we proposed an improved colour image quantization scheme based on predictive coding. Since the neighbouring colour pixels are quite similar in most colour images, the similarity among the encoded pixels is exploited. In the proposed scheme the encoded distinct neighbouring colours are collected to form a smaller state-palette. If the closest colour in the state-palette is quite similar to the current encoding colour pixel, the index of the closest colour in the state-palette is recorded. Otherwise, the closest colour in original colour palette for the current encoding colour pixel is searched and the corresponding index is recorded. The experimental results show that the proposed method achieves good image qualities while requiring much lower bit rates for colour image compression.     

Investigation of Chinese skin colour and appearance for skin colour reproduction

A Chinese skin colour database is established based on measurements taken from nine bodies areas of 202 Chinese individuals to move towards accurate skin colour reproduction. The colour appearance of each skin point is predicted, and a comprehensive colour gamut for Chinese skin is determined. A consistent colour shift between facial and arm colours is identified, in which facial colour tends to be more reddish, more colourful, and darker than arm colour. Moreover, Chinese females are found to have lighter, paler, and more yellowish skin than Chinese males. Variations in Chinese skin colour are quantified, and body area differences and gender differences are shown to have significant effects on Chinese skin colour.     

The physics of colour vision

Investigation of human colour vision relies primarily upon psycho-physical methods which require active observer participation in the experiments. The principal results of such experiments are stated and discussed in relation to the functional organisation of human colour vision. Generally, objective techniques, such as electro-physiology, are employed in the study of colour vision responses in non-human vertebrate species. The structural and functional organisation of vertebrate colour vision as revealed by these objective methods is described and the relationship between objective and psycho-physical results examined. Other sections of the article are concerned with defective colour vision and with parametric variations in normal colour vision. It is concluded that a reasonably consistent scheme for the organization of human colour vision emerges from the various types of experimental investigation, and that this scheme is adequate for the interpretation of a variety of colour vision phenomena.     

The colour wheels of art, perception, science and physiology

Colour is not the domain of any one discipline be it art, philosophy, psychology or science. Each discipline has its own colour wheel and this presentation examines the origins and philosophies behind the colour circles of Art, Perception, Science and Physiology (after image) with reference to Aristotle, Robert Boyle, Leonardo da Vinci, Goethe, Ewald Hering and Albert Munsell.The paper analyses and discusses the differences between the four colour wheels using the Natural Colour System® notation as the reference for hue (the position of colours within each of the colour wheels). Examination of the colour wheels shows the dominance of blue in the wheels of art, science and physiology particularly at the expense of green.This paper does not consider the three-dimensionality of colour space its goal was to review the hue of a colour with regard to its position on the respective colour wheels.     

Is colour cognitive?

In recent years, colour-vision abilities have been rather generously ascribed to various invertebrates and even bacteria. This uncertainty of when to diagnose colour vision stems in part from confusing what colour vision can do with what it is. What colour vision can do is discriminate wavelength independent of intensity. However, if we take this as a definition of what colour vision is, then we might be obliged to conclude that some plants and bacteria have colour vision. Moreover, there is a similar confusion of what are necessary and what are sufficient mechanisms and behavioural abilities for colour vision. To humans, seeing in colour means seeing an image in which objects/lights have chromatic attributes—in contrast to the sensation that we have when viewing monochrome movies, or our experience in dim light when only rod vision is possible. The necessary basic equipment for this is to have at least two types of photoreceptors that differ in spectral sensitivity, and at least one type of spectrally opponent cell to compare the signals from the photoreceptors. Clearly, however, a necessary additional prerequisite for colour vision is to have vision, which entails the identification of shapes, sizes and locations of objects in the world. Thus, if an animal has colour vision, it should see an image in which distinct objects/lights have colour attributes. This distinguishes colour vision from wavelength discrimination, but also from what has historically been called wavelength-specific behaviour: a type of behaviour triggered by fixed configurations of spectral receptor signals; however, we discuss difficulties in diagnosing wavelength-specific behaviour as an indicator of the absence of colour vision. Finally, we discuss whether colour vision, by definition, contains a cognitive dimension for ordering and classifying perceptual experience.     

Multicolour spatial frequency analysis by optical multiplexing

The Fourier transforms of colour transparencies have been separated spatially according to their colour content. The use of a different spatial carrier for each colour enables simultaneous detection of the spectra as well as reconstitution of an image after different spatial filtering processes have been performed on different colour spectra.     

Behaviour of gluons at high temperature

The screening of colour electric and magnetic fields and plasma oscillations in a high-temperature gluon plasma are investigated using linear response theory and self-consistent nonperturbative solutions to the Schwinger-Dyson equation. Static electric fields are screened, with

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. This result is proven to be gauge invariant in two ways: by computing π₀₀ in temporal axial, Coulomb and covariant gauges, and by computing the physical free energy of a heavy quark pair in the plasma in temporal axial gauge. To order g³ static magnetic fields are not screened.     

Non-renormalization of the weak vertex in gauge theories with integrally charged quarks

We give current algebra arguments to show that toO(α) the colour octet vertices do not renormalize the effective weak vertex between colour singlet hadrons in models with broken colour symmetry. The result does not depend on the details of the mixing between colour gluons and electro-weak bosons.     

Colour symmetry double point groups

Thirty four distinct composition series arising out of the 32 crystallographic double point groups are employed to re-derive in a simple and elegant fashion all the 169 distinct colour symmetry groups generated by the 32 double point groups, exploiting the idea of colour generators. The advantage of the method employed and some possible applications of these colour groups are discussed. The resulting colour groups are tabulated.     

颜色温度和相关色温的不确定度评定方法

颜色温度和相关色温是光源的重要参量。从色品坐标(u,v)到颜色温度和相关色温的计算过程比较复杂,很难依据国际标准化组织推荐的不确定度评定方法进行分析。介绍了从光谱辐射功率和色品坐标(u,v)的不确定度出发,按照国际标准化组织的推荐方法,得到更为科学合理的颜色温度和相关色温的不确定度评定方法。针对新的国家颜色温度副基准,分别采用基于数学模型的精确方法、近似方法和几何方法对其不确定度进行了评价,并与传统方法进行了比较。采用传统方法得到的计算结果偏高,这是因为传统的计算方法很大程度上基于实验和经验估计,没有将颜色温度的不确定度与光谱辐射功率和色品坐标(u,v)的不确定度之间建立明确的数学关联,在分析过程中存在对某一不确定度源进行重复计算的可能。所述的数学推导方法相对传统方法更为科学合理。