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.     

Those Wonderful Pioneer Years of SSRL: A Personal Reflection

It is a rare moment in the history of science when a new capability is born that transforms our ability to “see” what is happening in the world in which we live. The use of the light emitted from accelerating electrons as they are bent by magnetic fields that was pioneered at SSRL in the 1970s is not just another example of this, but arguably is the most important development in the history of science in enabling us to “see” the world of electrons and atoms. There is, in addition, a special feature of the new capability enabled by synchrotron radiation: it is likely to remain, in the future, the best way to see the microscopic world forever. This is because the light used to “see” does not only have all the intensity one needs, but also because all its properties can be adjusted so as to provide the ideal illumination for the particular thing one wants to “see.” Thus, literally what was born at SSRL, which has since then been and will be continually improved, will forever provide our species the ability to “see” and understand the microscopic world in which we live.     

Waves and rays in uniaxial birefringent crystals

In this paper, we present a more elaborate and complete way of the formalism that we have developed in successive steps for ray tracing through uniaxial birefringent media in view of the optical design. With the obtained formulas we analyze in detail what we see through a cleavage calcite crystal.     

How have they started? – A brief guide for pedestrians

I shall present a very brief summary of subjects selected from what Prof. Akito Arima has done in the past years. I will focus on the initial works on the configuration mixing and on the Interacting Boson Model. Since there are many literatures on these subjects, I shall concentrate what have been done at the initial or at the pre-history stages. By doing this, we shall see how Prof. Akito Arima started from the scratch.     

What Makes a Theory Testable, or Is Intelligent Design Less Scientific Than String Theory?

I compare the theory of intelligent design to string theory to see on what basis, if any, only the former can be justifiably excluded as being scientific.We shall see that the classic criterion of testability or falsifiability is sometimes not so straightforward, and that there are other criteria to help us make such a distinction.     

The importance of self-consistency in determining interface properties of SIN and DIN structures

We develop a method to solve the Bogoliubov–de Gennes equation for superconductors self-consistently, using the recursion method. The method allows the pairing interaction to be either local or nonlocal corresponding to s-and d-wave superconductivity, respectively. Using this method, we examine the properties of various SIN and DIN interfaces. In particular, we self-consistently calculate the spatially varying density of states and the superconducting order parameter. We see that changing the strength of the insulating barrier at the interface, does not, in the case of an s-wave superconductor, dramatically change the low-energy local density of states in the superconducting region near the interface. This is in stark contrast to what we see in the case of a DIN interface where the local particle density of states is changed dramatically. Hence we deduce that in calculating such properties as the conductance of SIN and DIN structures it is far more important to carry out self-consistent calculations in the d-wave case.     

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.     

Experimental evidence for Raman-induced limits to efficient squeezing in optical fibers

We report new experiments on polarization squeezing using ultrashort photonic pulses in a single pass of a birefringent fiber. We measure what is to our knowledge a record squeezing of -6.8+/-0.3 dB in optical fibers, which when corrected for linear losses is -10.4+/-0.8 dB. The measured polarization squeezing as a function of optical pulse energy, which spans a wide range from 3.5-178.8 pJ, shows a very good agreement with the quantum simulations, and for the first time we see the proof experimentally that Raman effects limit and reduce squeezing at high pulse energy.     

Unified theory of bound and scattering molecular Rydberg states as quantum maps

Using a representation of multichannel quantum defect theory in terms of a quantum Poincaré map for bound Rydberg molecules, we apply Jung's scattering map to derive a generalized quantum map, that includes the continuum. We show that this representation not only simplifies the understanding of the method, but moreover produces considerable numerical advantages. Finally we show under what circumstances the usual semi-classical approximations yield satisfactory results. In particular we see that singularities that cause problems in semi-classics are irrelevant to the quantum map.     

Detection of coloured tracks of heavy ion particles using photographic colour film

A photographic colour film, which was exposed to heavy ions, reveals a coloured dye image of the ion tracks. Since the colour film consists of several layers and different colours appear on each layer, three-dimensional information on the tracks in the layers can be obtained by the colour image. Previously, we have reported the method for which the tracks in different colours represented differences of track depth and we also discussed the disadvantages of using commercial colour films. Here we present the procedure for a self-made photographic coating and the development formula which can overcome the disadvantages.     

Aesthetic fields—Null theory

We have studied aesthetic field theory in the case where all invariants constructed from Γ _jk ⁱ and involving g _ij are zero. We studied such a “null” theory in 1972, but the cases we cited were plagued with singularities. By introducing complex fields the situation with respect to singularities improved. Complex fields are consistent with the basic “aesthetic principles” we outlined earlier. Within our null theory we see in two-dimensional spacetime a scattering of particles that was more involved than what we had seen before (regardless of dimensions). We see creation and annihilation of particles out of the vacuum. We also see a three-particle system within a small region of spacetime. In three spacetime dimensions we see a bound two-particle system. Another solution suggests a bound three-particle system. As well as we can tell the particles stay together (confinement) and do not give problems with attenuation. We observe in three dimensions one of the bound systems moving along a definite path in time. The four-dimensional spacetime results are not clear at this point. Whether “topological” bound systems of three particles exist has yet to be determined. A map in the four-dimensional case indicates a planar three maxminima confluence and the suggestion of a second such confluence.     

Ultrafast α-like relaxation of a fragile glass-forming liquid measured using two-dimensional infrared spectroscopy

Ultrafast two-dimensional infrared (2D-IR) spectroscopy is used to study the picosecond dynamics of a vibrational probe molecule dissolved in a fragile glass former. The spectral dynamics are observed as the system is cooled to within a few degrees of the glass transition temperature (T(g)). We observe nonexponential relaxation of the frequency-frequency correlation function, similar to what has been reported for other dynamical correlation functions. In addition, we see evidence for α-like relaxation, typically associated with long-time, cooperative molecular motion, on the ultrafast time scale. The data suggests that the spectral dynamics are sensitive to cooperative motion occurring on time scales that are necessarily longer than the observation time.     

Two‐beam multiplexed CARS based on a broadband oscillator

A two‐beam multiplexed coherent anti‐Stokes Raman scattering (CARS) microscopy setup is demonstrated by using a broadband (BB) Ti:sapphire oscillator without using any specialty fibres. A well‐defined spectral structure of the source leads to a delay‐sensitive CARS measurement in two‐colour CARS and also provides an efficient means of obtaining three‐colour CARS signals combined with the dispersion compensation of the BB pulse. Our result implies that the background suppression is limited by the onset of the spurious signals caused by the different CARS process, qualitatively differing from what is typically observed in the CARS microscopy. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantitative properties of colour singlet clusters in QCD jets

Using a Monte Carlo technique we have made detailed calculations of the properties of colour singlet clusters in QCD jets, first discussed by Amati and Veneziano. Although the results confirm a mass damping for colour singlets, we find that, quantitatively, it is not enough to justify a phenomenological use of colour singlets as an intermediate step in the materialization of QCD quanta into hadrons.     

Colour superconductivity in finite systems

We have studied the effects of finite size on the two flavor colour superconducting state. Since the baryon number in the BCS state is only fixed on average, we have projected the state onto a fixed baryon number. The resulting state has been then projected onto a colour-singlet state, by integrating onto the colour group manifold. The effects of both projections have been evaluated numerically.     

Symmetry-increasing bifurcation of chaotic attractors

Bifurcation in symmetric is typically associated with spontaneous symmetry breaking. That is, bifurcation is associated with new solution having less symmetry.In this paper we show that symmetry-increasing bifurcation in the discrete dynamics of symmetric mappings is possible (and is perhaps generic). The reason for these bifurcations may be understood as follows. The existence of one attractor in a system with symmetry gives rise to a family of conjugate attractors all related by symmetry. Typically, in computer experiments, what we see is a sequence of symmetry-breaking bifurcations leading to the existence of conjugate chaotic attractors. As the bifurcation parameter is varied these attractors grow in size and merge leading to a single attractor having greater symmetry.We prove a theorem suggesting why this new attractor should have greater symmetry and present a number of striking examples of the symmetric patterns that can be formed by iterating the simplest mappings on the plane with the symmetry of the regular m-gon. In the last section we discuss period-doubling in the presence of symmetry.     

Resurgent transseries & Dyson–Schwinger equations

We employ resurgent transseries as algebraic tools to investigate two self-consistent Dyson–Schwinger equations, one in Yukawa theory and one in quantum electrodynamics. After a brief but pedagogical review, we derive fixed point equations for the associated anomalous dimensions and insert a moderately generic log-free transseries ansatz to study the possible strictures imposed. While proceeding in various stages, we develop an algebraic method to keep track of the transseries’ coefficients. We explore what conditions must be violated in order to stay clear of fixed point theorems to eschew a unique solution, if so desired, as we explain. An interesting finding is that the flow of data between the different sectors of the transseries shows a pattern typical of resurgence, i.e. the phenomenon that the perturbative sector of the transseries talks to the nonperturbative ones in a one-way fashion. However, our ansatz is not exotic enough as it leads to trivial solutions with vanishing nonperturbative sectors, even when logarithmic monomials are included. We see our result as a harbinger of what future work might reveal about the transseries representations of observables in fully renormalised four-dimensional quantum field theories and adduce a tentative yet to our mind weighty argument as to why one should not expect otherwise.     

Critical behaviour in very pureNi−Ta systems

Conclusion We use the perturbed angular correlation technique to follow the behaviour of the m agnetic hyperfine field on¹⁸¹Ta in nickel in the critica region of the matrix. Contrary to what is expected, we observe that the critical exponent associated to the hyperfine field is different from the critical exponent associated to the bulk magnetization. Because the concentrations of the various impurities are very low, we think that the explantation of the phenomenon is to be found is the framework of a one-impurity model interacting with the surrounding spins via an isotropic exchange energy. This problem, as one can see, bear some similarities with the Kondo problem.A extended version of this paper has been submitted for publication elsewhere.     

The use and misuse of coloured light in the urban environment

The last few years have seen a huge increase in the transfer of coloured architectural lighting, derived from entertainment and theatre, into the urban and exterior environment. Part of the reason for this is that in the last 15 yr or so, there have been a number of important introductions in coloured lighting technology. These have transformed lighting practice, and while their widespread introduction is seen by some as an enrichment of the urban fabric, others see it as presenting considerable dangers, in terms of aesthetics, perception and in terms of civic identity. Its negative effects on the urban environment have been termed ‘colour blight’.In this paper, the range of coloured lighting technologies is surveyed and other causes for the increase in coloured lighting are also discussed, together with the problems and benefits involved. Finally, some tentative means are put forward for resolving the problems caused by ‘colour blight’. Current good practice is illustrated by the author's own experience, including his consultancy's participation in a number of urban lighting strategies in the UK and elsewhere. This work involves implementation of a comprehensive lighting plan for the historic city of York, as part of the Urban Lighting Group consortium of three lighting design practices.     

Inclusive photo- and electroproduction of pions in the triple Regge region

We develop a Regge pole expansion including spin for inclusive photo- and electroproduction of pions in the photon fragmentation region and see to what extent the available data at intermediate energies can be explained in terms of Regge poles alone. It is shown that a pure Regge pole model is not adequate, although some qualitative features are reproduced.