Clifford Space as a Generalization of Spacetime: Prospects for QFT of Point Particles and Strings

The idea that spacetime has to be replaced by Clifford space (C-space) is explored. Quantum field theory (QFT) and string theory are generalized to C-space. It is shown how one can solve the cosmological constant problem and formulate string theory without central terms in the Virasoro algebra by exploiting the peculiar pseudo-Euclidean signature of C-space and the Jackiw definition of the vacuum state. As an introduction into the subject, a toy model of the harmonic oscillator in pseudo-Euclidean space is studied.     

Quantum Groups and Double Quiver Algebras

For a finite dimensional semisimple Lie algebra and a root q of unity in a field k, we associate to these data a double quiver . It is shown that a restricted version of the quantized enveloping algebras is a quotient of the double quiver algebra .*The author is partially supported by the National Science Foundation of China (Grant. 10271014) and Natural Science Foundation of Beijing City (grant. 1042001)     

The extended trace identity and its application

The trace identity is extended to the general loop algebra. The Hamiltonian structures of the integrable systems concerning vector spectral problems and the multi-component integrable hierarchy can be worked out by using the extended trace identity. As its application, we have obtained the Hamiltonian structures of the Yang hierarchy, the Korteweg-de--Vries (KdV) hierarchy, the multi-component Ablowitz--Kaup--Newell--Segur (M-AKNS) hierarchy, the multi-component Ablowitz--Kaup--Newell--Segur Kaup--Newell (M-AKNS--KN) hierarchy and a new multi-component integrable hierarchy separately.     

表征体元尺度渗流的离散统一动理学格式

结合表征体元尺度的通用渗流模型,提出离散统一动理学格式（DUGKS）渗流方法,分别用均匀网格和非均匀网格计算二维Poiseuille、Couette、方腔流等经典渗流问题,检验DUGKS渗流方法的有效性和非均匀网格应用的优势,将DUGKS渗流方法应用到裂缝系统中.     

Photoelectric Properties of the In/CuIn3Se5 and In/CuGa3Se5 Structures

Using the method of oriented crystallization of a melt (a vertical variant), we grew homogeneous single crystals of the ternary compounds CuIn₃Se₅ and CuGa₃Se₅. Photosensitive structures based on them were created for the first time, the spectral dependences of the relative quantum efficiency of the phototransformation of structures were investigated, and the energy gap width of the ternary compounds was determined. It is established that the CuIn₃Se₅ and CuGa₃Se₅ compounds are materials with direct interband transitions. We show that the structures created can be used as wideband photoconverters of natural radiation.     

Self-Trapping in Discrete Nonlinear Schrdinger Equation with Next-Nearest Neighbor Interaction

The dynamical self-trapping of an excitation propagating on one-dimensional of different sizes with nextnearest neighbor (NNN) interaction is studied by means of an explicit fourth order symplectic integrator. Using localized initial conditions, the time-averaged occupation probability of the initial site is investigated which is a function of the degree of nonlinearity and the linear coupling strengths. The self-trapping transition occurs at larger values of the nonlinearity parameter as the NNN coupling strength of the lattice increases for fixed size. Furthermore, given NNN coupling strength, the self-trapping properties for different sizes are considered which are some different from the case with general nearest neighbor (NN) interaction.     

Homogeneous Isotropic Turbulence: Geometric and Isometry Properties of the 2-point Velocity Correlation Tensor

The emphasis of this review is both the geometric realization of the 2-point velocity correlation tensor field B_ij (x,x′,t) and isometries of the correlation space K³ equipped with a (pseudo-) Riemannian metrics ds²(t) generated by the tensor field. The special form of this tensor field for homogeneous isotropic turbulence specifies ds²(t) as the semi-reducible pseudo-Riemannian metric. This construction presents the template for the application of methods of Riemannian geometry in turbulence to observe, in particular, the deformation of length scales of turbulent motion localized within a singled out fluid volume of the flow in time. This also allows to use common concepts and technics of Lagrangian mechanics for a Lagrangian system (M^t, ds²(t)), M^t ? K³. Here the metric ds²(t), whose components are the correlation functions, evolves due to the von Kármán-Howarth equation. We review the explicit geometric realization of ds²(t) in K³ and present symmetries (or isometric motions in K³) of the metric ds²(t) which coincide with the sliding deformation of a surface arising under the geometric realization of ds²(t). We expose the fine structure of a Lie algebra associated with this symmetry transformation and construct the basis of differential invariants. Minimal generating set of differential invariants is derived. We demonstrate that the well-known Taylor microscale λ_g is a second-order differential invariant and show how λ_g can be obtained by the minimal generating set of differential invariants and the operators of invariant differentiation. Finally, we establish that there exists a nontrivial central extension of the infinite-dimensional Lie algebra constructed wherein the central charge is defined by the same bilinear skew-symmetric form c as for the Witt algebra which measures the number of internal degrees of freedom of the system. For turbulence, we give the asymptotic expansion of the transversal correlation function for the geometry generated by a quadratic form.     

Influence of doping of mercury atom(s) on optoelectronic properties of binary cadmium chalcogenides - A density functional theory based investigation with different exchange-correlation functionals and including spin-orbit coupling

Influence of doping of mercury atom(s) on optoelectronic properties of binary cadmium chalcogenides have been investigated theoretically by designing the mercury doped cadmium chalcogenide ternary alloys in B3 phase at some specific Hg-concentrations and studying their optoelectronic properties using DFT based FP-LAPW methodology. The structural properties are computed using WC-GGA, while spin-orbit coupling included electronic and optical properties are computed using TB-mBJ, EV-GGA, B3LYP and WC-GGA exchange-correlation functionals. In addition, electronic properties of mercury chalcogenides are calculated precisely using the GGA+U functionals. The concentration dependence of lattice parameter and bulk modulus of each of the Hg_xCd_1−xS, Hg_xCd_1−xSe, Hg_xCd_1−xTe alloy systems show almost linearity. For each of the alloy systems, band gap decreases almost linearly with increase in Hg-concentration in the unit cell and contribution from charge exchange to the band gap bowing is larger than that from for each of the volume deformation and structural relaxation. Also, covalent bonding exists between different constituent atoms in each compound. Optical properties of each specimen are computed from their spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption coefficient and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.     

Elastic,thermodynamic, electronic,and optical properties of recently discovered superconducting transition metal boride NbRuB:An ab-initio investigation

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation(GGA) and local density approximation(LDA) are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency(energy) dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.     

缓冲层对量子阱二能级系统中电子子带间跃迁光吸收的影响

由于ZnO缓冲层对纤锌矿ZnO/Mg_xZn_(1-x)O有限深单量子阱结构左垒的限制作用,导致阱和右垒的尺寸、Mg组分值等因素将影响系统中形成二能级.本文考虑内建电场、导带弯曲及材料掺杂对实际异质结势的影响,利用有限差分法数值求解Schr?dinger方程,获得电子的本征能级和波函数,探讨ZnO缓冲层对此类量子阱形成二能级系统的尺寸效应及三元混晶效应的影响;利用费米黄金法则探讨缓冲层、左垒、阱及右垒宽度和三元混晶效应对此类量子阱电子子带间跃迁光吸收的影响.计算结果显示:对于加入ZnO缓冲层的ZnO/Mg_xZn_(1-x)O有限深单量子阱二能级系统,左垒宽度临界值会随着阱宽和Mg组分值的增大而逐渐减小,随着右垒宽度和缓冲层厚度的增大而逐渐增大;量子阱中电子子带间跃迁光吸收峰会随着左垒、右垒尺寸以及Mg组分的增大发生蓝移,随着阱宽增大而发生红移.本文所得结果可为改善异质结器件的光电性能提供理论指导.