On the problem of singular charge density at the center of pion

We generalize and analyze the expression for the quark density of a pion with allowance for the quantum nature of the impact parameter in a region of small phase space volume. As a result, there is no singularity at the center of a pion.     

Spectral description of fluctuating electromagnetic fields of solids using a self-consistent approach

A new way to evaluate the spectral-correlation properties of thermal fields of solids is suggested. The principal element here is the surface linear response function of an inhomogeneous electron subsystem of solids. Along with straightforward calculations using the known response functions, the suggested method allows calculating the response functions self-consistently based on the time dependent density functional theory. The self-consistent calculation of the linear response function followed by an application of the fluctuation–dissipation theorem yields spectral power densities of the fluctuating electromagnetic fields.     

Orbital currents and charge density waves in a generalized Hubbard ladder

We study a generalized Hubbard model on the two-leg ladder at zero temperature, focusing on a parameter region with staggered flux (SF)/d-density wave (DDW) order. To guide our numerical calculations, we first investigate the location of a SF/DDW phase in the phase diagram of the half-filled weakly interacting ladder using a perturbative renormalization group (RG) and bosonization approach. For hole doping δ away from half-filling, finite-system density-matrix renormalization-group (DMRG) calculations are used to study ladders with up to 200 rungs for intermediate-strength interactions. In the doped SF/DDW phase, the staggered rung current and the rung electron density both show periodic spatial oscillations, with characteristic wavelengths 2/δ and 1/δ, respectively, corresponding to ordering wavevectors 2k_F and 4k_F for the currents and densities, where 2k_F = π (1 − δ). The density minima are located at the anti-phase domain walls of the staggered current. For sufficiently large dopings, SF/DDW order is suppressed. The rung density modulation also exists in neighboring phases where currents decay exponentially. We show that most of the DMRG results can be qualitatively understood from weak-coupling RG/bosonization arguments. However, while these arguments seem to suggest a crossover from non-decaying correlations to power-law decay at a length scale of order 1/δ, the DMRG results are consistent with a true long-range order scenario for the currents and densities.     

长直带电导体柱的电场及其电荷面密度

通过保角变换法及其变换关系,求解长直带电导体柱的电场分及电荷面密度,利用数学软件MATLAB对其场分布进行数值模拟,并绘制出电荷面密度的分布曲线.     

Basic properties of nonlinear surface charge waves at a plasma boundary

The nonlinear properties of surface charges are here analyzed under ideal conditions. We thus deduce a new single equation from the wellknown equations which govern the cold electron plasma motion. Simple formulas that describe the propagation of surface charge perturbations along the plasma boundary are also found.     

电磁场统一性质的三维描述

论述了电场与磁场本质上的统一性质,构造了三维空间中电磁场的统一场量,给出它的方程、场量的模方与能量和动量的关系,发现三维空间中的统一场量自身的标积竟然是相对论变换下的不变量．     

On the charge density modulation in the bunch by the interaction with electromagnetic wave

The efficiency of the charge density modulation of an electron bunch in the field of a linearly polarized monochromatic electromagnetic wave propagating oppositely to the bunch motion is considered. It is shown that as a result of the bunch-wave interaction the coherently radiating bunches can be obtained.     

On the solutions of the coupled system of oscillators and electromagnetic fields excited by an external charge

A systematic study of the longitudinal, transverse and total solutions of a coupled system of oscillators and electromagnetic fields in the presence of an external point charge is carried out. The space-time dependence of the solutions as well as their values in specific cases and asymptotic behavior are analyzed. It is shown that, in general, the longitudinal fields show two well-defined contributions: (a) a symmetric field surrounding the particle and carried convectively which is interpreted as a screening field. (b) an excitation defined in principle in a whole semispace and identified with an oscillator plasma wave which corresponds to the excitation predicted in A. Bohr's microscopic theory of energy losses, although showing somewhat different properties. The transverse solutions appear as differences between the fields given in Fermi's macroscopic theory of energy losses and the longitudinal solutions. Using methods of complex variable theory it is shown how we can separate the total perturbations created by the particle in a medium represented by oscillators into three intimately related contributions: screening, oscillator-plasma excitation and Cherenkov radiation. The space-time configuration of these fields as well as their relation to the longitudinal solutions and their evolution for different ranges of the velocity of the particle is given. The problem of the energy loss associated to the creation of the plasma wave is treated.     

Unified equation of motion of a test charge in electromagnetic and gravitational fields

This work starts by generalizing in a gravitational field the fundamental quantum mechanical commutation relations between the coordinates of a charged test particle and its momentum. Assuming that the components of the momentum of this test charge obey a noncommutative algebra in the presence of an electromagnetic field, it is proved that the commutator can be identified with the electromagnetic field tensor. Using these results, the equation of motion of this charged object in the presence of both the electromagnetic and gravitational fields is derived from their field equations. In this work, the laws of motion of a particle in the electromagnetic and gravitational fields has been unified with the field equations. Although the field equations themselves are not directly unified, this work strongly suggests that the scheme may act as a possible framework for the unification of at least gravitational and electromagnetic interactions.     

Effect of electromagnetic perturbation on charge imbalance in a superconductor: A two-fluid description

Using a generalized two-fluid pictures for the charge of superconductor and ordinary Boltzmann equation for quasiparticle excitations, the effect of frequency and wave-vector dependent electromagnetic perturbation on charge imbalance near transition temperatureT _C is studied. In a situatiod where both the effective charge and distribution function of quasiparticles deviate from their equilibrium values, the charge imbalance is shown to possess a propagating solution at frequencies greater than inelastic scattering rate. In situations where charge imbalance is created by injection of quasiparticles, the charge imbalance relaxation rate is shown to decrease. We also study the effect of applied perturbation on quasiparticle diffusion length and hence on superconductor—normal interface boundary resistance.     

Quantization of the band at the surface of charge density wave material 2H-TaSe_2

By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_2.We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_z direction.The quantized sub-bands shift upward towards E_F while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_2,our experiment may ignite the interest in understanding the CDW mechanism in this family.     

On the instability against the surface charge of a liquid meniscus at the end of a capillary

The subject of consideration is instability of the flat meniscus of a viscous liquid at the end of a capillary in the gravitational field and an electrostatic field when the symmetry axis of the capillary is arbitrarily oriented relative to the direction of free-fall acceleration. It is shown that, if the electrostatic field strength is high, the development of meniscus instability does not depend on the orientation of the capillary. The instability growth rate versus wavenumber dependence for annular waves of different types on the meniscus surface is found to be nonmonotonic.