Correlations for the orthogonal-unitary and symplectic-unitary transitions at the hard and soft edges

For the orthogonal-unitary and symplectic-unitary transitions in random matrix theory, the general parameter dependent distribution between two sets of eigenvalues with two different parameter values can be expressed as a quaternion determinant. For the parameter dependent Gaussian and Laguerre ensembles the matrix elements of the determinant are expressed in terms of corresponding skew-orthogonal polynomials, and their limiting value for infinite matrix dimension are computed in the vicinity of the soft and hard edges respectively. A connection formula relating the distributions at the hard and soft edge is obtained, and a universal asymptotic behaviour of the two point correlation is identified.     

Comparison between the symmetric fission and fusion paths

The symmetric fission path leading to smooth extended shapes and the fusion or new fission path going through the two tangent sphere configuration are investigated within the liquid-drop model including the nuclear proximity energy. Analytical formulae are given for the various shape-dependent functions which govern the dynamics. The quadrupole moment, the perpendicular moment of inertia and the Coulomb energy are similar in the two paths. In contrast, the neck radius, the rupture point between the fragments, the parallel and effective moments of inertia, the surface energy and the critical angular momentum against fission are quite different in the two valleys. The introduction of the proximity energy strongly lowers the deformation energy in the fusion valley and for the light, medium and very heavy nuclei the barrier heights are nearly equal in the two paths. This flattening of the potential surface by the proximity forces allows to better understand the sudden transition between the one- and two-body configurations.     

Jump of the minimal site and a new correlation function in the Bak-Sneppen model

A new type of spatio-temporal correlation function for the process approaching the self-organized criticality is investigated within the Bak-Sneppen model for biological evolution. In terms of the “directional shorter distance” between the two sites with minimum fitness at two successive updates, the correlation function is defined and studied numerically for the nearest- and random-neighbor versions of the model. Qualitatively different behaviors of the jump of the minimal site in the two models are presented, and the behaviors of the correlation functions are shown also different. Received 14 April 2001 and Received in final form 28 June 2001     

Violations of the Pauli principle and the interior of the sun

The consequences of a violation of the Pauli principle for the physics of the solar interior are explored. It is found that a bound state of two protons becomes possible. This leads to an increase in the rate of hydrogen burning in the sun. Because a very large cross section for this reaction is in clear contradiction with the theory of stellar structure when compared with observations of solar luminosity, radius and mechanical oscillations, stringent limits on a violation of the Pauli principle in the two nucleon system can be given. However, a very small violation of the Pauli principle in the two nucléon system might solve the longstanding solar neutrino problem.     

含硫氨基酸与本征及缺陷石墨烯表面的相互作用

半胱氨酸及蛋氨酸是人体的两种含硫氨基酸,在生物活性中发挥着巨大的作用.本研究采用密度泛函理论方法对以上两种氨基酸在本征及缺陷石墨烯表面的吸附机理进行了详细研究.主要考虑了两种吸附体系:半胱氨酸及蛋氨酸平躺在两种石墨烯表面;两种氨基酸垂直地放置于两种石墨烯表面,且含硫的基团靠近表面.研究结果表明,半胱氨酸及蛋氨酸初始构型对它们之间的相互作用有一定的影响.两种氨基酸平躺时有较大的吸附能.此外,吸附能的结果显示两种氨基酸可以更好的与缺陷石墨烯表面紧密结合.同时,蛋氨酸与本征及缺陷石墨烯相互作用均大于半胱氨酸与本征及缺陷石墨烯相互作用.模拟结果有望为含硫氨基酸的石墨烯传感器提供有用的指导.     

Particle-hole symmetry and the Pfaffian state

We show that the particle-hole conjugate of the Pfaffian state-or "anti-Pfaffian" state-is in a different universality class from the Pfaffian state, with different topological order. The two states can be distinguished easily by their edge physics: their edges differ in both their thermal Hall conductance and their tunneling exponents. At the same time, the two states are exactly degenerate in energy for a nu=5/2 quantum Hall system in the idealized limit of zero Landau level mixing. Thus, both are good candidates for the observed sigma_{xy}=5/2(e;{2}/h) quantum Hall plateau.     

Vacuum renormalization of the chiral-sigma model and the structure of neutron stars

Vacuum renormalization corrections are calculated for normal nuclear matter and neutron star matter in the chiral-sigma model. The theory is generalized to include hyperons in equilibrium with nucleons and leptons. The equations of state corresponding to two compression moduli, a “stiff” and “soft” one for nuclear matter, are studied. It is shown that fully one half the mass of a neutron star at the limiting mass is composed of matter at less than twice nuclear density. Neutron star masses are therefore moderately sensitive to the properties of matter near saturation and to the domain of the hyperons, but dominated by neither. The predictions for the two equations of state are compared with observed neutron star masses, and only the stiffer is compatible.     

对单轴晶体中光的性质和双折射问题的几点讨论

指出了关于光在单轴晶体中的传播、偏振及双折射问题中的几个模糊概念或论点;证明了在单轴晶体中属同一波矢的两个线偏振光光矢量的偏振方向也是相互垂直的,而且此两光的主平面是相互重合的;分析了在双折射教学中尚存的不足之处和个别欠妥的提法;指出在讨论双折射问题时必须加入适当的基础理论,而仅用定性作图法将对理解掌握该部分内容带来某些弊端．     

Existence and Order of the Phase Transition of the Ising Model with Fixed Magnetization

Properties of the two dimensional Ising model with fixed magnetization are deduced from known exact results on the two dimensional Ising model. The existence of a continuous phase transition is shown for arbitrary values of the fixed magnetization when crossing the boundary of the coexistence region. Modifications of this result for systems of spatial dimension greater than two are discussed.     

Combining the sone and phon scales

Some of the conceptual implications of the widespread use of the phon curves are discussed and a plot is presented in ‘carpet graph’ form. Arguments for and against use of the sone scale are summarised, followed by a discussion of the relationship between the two scales. To illustrate the implications of this relationship, the effect is shown of combining the information contained in the two scales into a single plot. Finally, to overcome a commonly heard practical objection to the use of the normal sone scale, a logarithmic form is suggested.     

In-line holography and the assessment of aerosols

Basic requirements for any apparatus designed to measure aerosol particles are reviewed. In-line holography is demonstrated to be a powerful tool in the assessment of aerosols and two dissimilar applications are described. The fundamental methods for producing holograms suitable for automatic analysis are given, with particular emphasis on exposure control.     

On the relation between the fractional Brownian motion and the fractional derivatives

The definition and simulation of fractional Brownian motion are considered from the point of view of a set of coherent fractional derivative definitions. To do it, two sets of fractional derivatives are considered: (a) the forward and backward and (b) the central derivatives, together with two representations: generalised difference and integral. It is shown that for these derivatives the corresponding autocorrelation functions have the same representations. The obtained results are used to define a fractional noise and, from it, the fractional Brownian motion. This is studied. The simulation problem is also considered.     

连续光在生物组织中能流率分布的漫射近似和模拟

分析了半无限大介质漫射近似不同边界条件的镜像光源结构,用镜像光源的方法给出了连续光入射时稳态能流率分布的漫射近似表达式,并用Monte Carlo方法对能流率分布进行模拟,分析了两种模型能流率分布的特点及其形成的机理;用Monte Carlo模拟结果检验了能流率分布漫射近似的精度,结果表明:漫射近似采用EBC边界条件的结果有较高的精度和计算较简单等优点,为能流率分布的快速准确计算提供了依据.     

On the equivalence between the Landau-Migdal and the Bohr-Mottelson interactions

The predictions given by the Landau-Migdal and the Bohr-Mottelson interactions for M1 and Gamow-Teller transitions and for the core polarization efiects in magnetic moments are investigated. While reasonably good correspondence is found between the two forces as concerns M1 and Gamow-Teller excitations, they give dramatic different predictions for magnetic moments.     

超声波电发生器的最大输出功率和效率

本文从电路理论中的最大功率传输定理出发，分析了超声波电发生器与普通电源的异同，提出了最大功率传输定理的扩展条件，从而将一般电源的匹配和超声波发生器的匹配这两种概念统一起来。文章应用扩展后的最大功率传输定理，从一个新的角度对超声波电发生器的最大输出功率和效率进行了分析，得到与图解法等其他方法相同的结果。     

On the double-grid excitation of linear and nonlinear ion-acousticwaves

A series of experiments has been performed in which the mechanism for the excitation of linear and nonlinear ion-acoustic waves from a structure consisting of two large parallel fine-mesh grid structures are considered. It is observed that the structure will launch a burst of ions through a velocity modulation mechanism if the two grids are sufficiently close together. A klystron-bunching model that was proposed previously appears to be valid for this launching mechanism     

Interaction between lexical and grammatical language systems in the brain

This review concentrates on two different language dimensions: lexical/semantic and grammatical. This distinction between a lexical/semantic system and a grammatical system is well known in linguistics, but in cognitive neurosciences it has been obscured by the assumption that there are several forms of language disturbances associated with focal brain damage and hence language includes a diversity of functions (phoneme discrimination, lexical memory, grammar, repetition, language initiation ability, etc.), each one associated with the activity of a specific brain area. The clinical observation of patients with cerebral pathology shows that there are indeed only two different forms of language disturbances (disturbances in the lexical/semantic system and disturbances in the grammatical system); these two language dimensions are supported by different brain areas (temporal and frontal) in the left hemisphere. Furthermore, these two aspects of the language are developed at different ages during child's language acquisition, and they probably appeared at different historical moments during human evolution. Mechanisms of learning are different for both language systems: whereas the lexical/semantic knowledge is based in a declarative memory, grammatical knowledge corresponds to a procedural type of memory. Recognizing these two language dimensions can be crucial in understanding language evolution and human cognition.     

Pin structures and the modified Dirac operator

General theorems on pin structures on products of manifolds and on homogeneous (pseudo-) Riemannian spaces are given and used to find explicitly all such structures on odd-dimensional real projective quadrics, which are known to be non-orientable (Cahen et al. 1993). It is shown that the product of two manifolds has a pin structure if and only if both are pin and at least one of them is orientable. This general result is illustrated by the example of the product of two real projective planes. It is shown how the Dirac operator should be modified to make it equivariant with respect to the twisted adjoint action of the Pin group. A simple formula is derived for the spectrum of the Dirac operator on the product of two pin manifolds, one of which is orientable, in terms of the eigenvalues of the Dirac operators on the factor spaces.