Unstable particles in a self-consistent field theory

We indicate how unstable particles can be introduced into the self-consistent field theory formulation of Umezawa where the equal-time commutation relations for Heisenberg fields are derived and not assumed. The Lee model is used to illustrate the results.     

A self-consistent field theory of crystals

A self-consistent theory of crystals is presented. The classical phenomenological theory of crystals is derived by means of the boson transformation method.     

The lamb shift in helium from a self-consistent field theory of electrodynamics

In this paper we present the results of an investigation of the finite self-consistent field theory of electrodynamics applied earlier to the calculation of the Lamb shift in hydrogen (Sachs & Schwebel, 1961; Sachs, 1972), now applied to the problem of the Lamb shift in the low-lying states of Helium. We construct the covariant nonlinear field equations of this theory for Helium, from the Lagrangian formalism. In the linear approximation, the Hamiltonian associated with this field theory for the two-electron atom is set up. It is equivalent to the Breit Hamiltonian plus two extra terms. This generalization is a direct consequence of the two-component spinor formalism of the factorization of the Maxwell theory of electromagnetism that is contained in this theory of electrodynamics (Sachs, 1971). Thus, the energy spectrum predicted for the Helium atom is the spectrum predicted by the Breit Hamiltonian, shifted by amounts in the different energy states according to the effects of the extra terms in the Hamiltonian. The latter can be associated with the corrections to the Helium spectrum that are conventionally attributed to the Lamb shift. The level shifts for the 1¹ S and 2³ S states are calculated using the Foldy-Wouthuysen transformation, with the generalization of Charplvy for the two-electron atom. The results are found to be in close agreement with the experimental values for the energy shifts not predicted by the Dirac theory, and with the theoretical values predicted by quantum electrodynamics.     

一种碳纳米管场效应管的HSPICE模型

为在HSPICE中建立一种计算简单且精度较高的碳纳米管场效应管 (carbon nanotube field effect transistor, CNTFET) 模型, 在CNTFET半经典建模方法的基础上, 分析了自洽电势与载流子密度之间的关系, 提出用线性近似进行拟合, 并推导了自洽电势的显式表达式, 从而避免了积分方程的迭代求解过程. 然后在HSPICE中建立了相应的CNTFET模型, 通过仿真比较, 结果表明该模型具有较高的精度, 用其构建的逻辑门电路能够实现相应逻辑功能, 且运算时间大为减少. 关键词： 碳纳米管场效应管 半经典模型 线性近似拟合 HSPICE仿真     

Equations with a self-consistent field in quantum-statistical theory of a crystal

A system of equations with a self-consistent field is derived for the density of particles in the quantum case. This system has periodic solutions for a crystal. Equations for the Fourier coefficients are deduced from these solutions and are used to find equations containing only the Fourier coefficients of the density. A method is also given for solving the initial system by an expansion in powers of the Planck constant ; the terms proportional to ² and ² are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 66–71, May, 1980.     

Electron field emission from single-walled carbon nanotube nonwoven

Field emission from single-walled carbon nanotube (SWNT) nonwoven has been investigated under high vacuum with different vacuum gaps. A low turn-on electric field of 1.05\,V/$\mu $m is required to reach an emission current density of 10 $\mu $A/cm$^{2}$. An emission current density of 10 mA/cm$^{2}$ is obtained at an operating electric field of 1.88\,V/$\mu $m. No current saturation is found even at an emission current of 5\,mA. With the vacuum gap increasing from 1 to 10 mm, the turn-on field decreases monotonically from 1.21 to 0.68\,V/$\mu $m, while the field amplification is augmented. The good field-emission behaviour is ascribed to the combined effects of the intrinsic field emission of SWNT and the waved topography of the nonwoven.     

Particle-like solutions in the theory of a relativistic self-consistent field

Interaction of an electron with its own electromagnetic field is described in terms of the Maxwell-Lorentz equations. The simplest possible state of the resulting self-consistent field is a free Proca-type vector mass field □u^μ?k²u^μ = 0.     

Thomas-Fermi theory for matter in a magnetic field as a limit of quantum mechanics

The Thomas-Fermi theory for electrons and fixed nuclei in a homogeneous magnetic field is shown to be a limit of quantum mechanics in the following sense: If the nuclear charges and the number of eletrons are multiplied by a, and the magnetic field by a ^4/3, then the ground-state energy, divided by a ^7/3, converges to the TF energy when a . A similar result holds also for the electronic density. This generalizes corresponding theorems for zero magnetic field due to Lieb, Simon, and Baumgartner.     

Magnetic charge in a nonassociative field theory

The violation of the Jacobi identity by the presence of magnetic charge is accomodated by using an explicity nonassociative theory of octonionic fields. It is found that the dynamics of this theory is simplified if the Lagrangian contains only dyonic charges, but certain problems in the constrained quantisation remain. The extension of these concepts to string theory may however resolve these difficulties.     

External field of a localized charge in unified field theory

The possibility of the existence of localized charged distribution giving rise to a special axially symmetric electrostatic field has been explored in Einstein's unified field theory [2]. The field equations have been studied in two particular cases. In one case the field equations have a solution representing flat space-time along with an electrostatic field which is constant in the direction of the axis of symmetry. For the other case the solution is non-existent.     

Thomas-Fermi model for an atom in a very strong magnetic field: thermal effects

Thermal effects on the Thomas-Fermi model for atoms in a very strong magnetic field are considered. The binding energy of the atom is calculated with the thermal effects taken into account.     

Coherent field emission from a multi-walled carbon nanotube with two open-ended branches

Interference fringes are obtained in a field-emission microscopy (FEM) study of a multi-walled carbon nanotube (MWCNT) with two open-ended branches. The FEM pattern, which is composed of three parallel streaks, can be interpreted by using classical Young's double-slit interference with the ends of the two MWCNT branches treated as two secondary sources of the electron wave. The origin of the coherency of the electron beams from the two branches is discussed on the basis of the quantitative analysis of the FEM pattern. The result suggests a new approach to obtaining a coherent electron source.     

Hydrodynamic self-consistent field theory for inhomogeneous polymer melts

We introduce a mesoscale technique for simulating the structure and rheology of block-copolymer melts and blends in hydrodynamic flows. The technique couples dynamic self-consistent field theory with continuum hydrodynamics and flow penalization to simulate polymeric fluid flows in channels of arbitrary geometry. We demonstrate the method by studying phase separation of an ABC triblock copolymer melt in a submicron channel with neutral wall wetting conditions. We find that surface wetting effects and shear effects compete, producing wall-perpendicular lamellae in the absence of flow and wall-parallel lamellae in cases where the shear rate exceeds some critical Weissenberg number.     

接触电阻对碳纳米管场发射的影响

基于改进的悬浮球模型,计算了碳纳米管和衬底间的接触电阻存在时碳纳米管顶端的局域电场, 并结合Fowler-Nordheim (F-N)场发射规律研究了接触电阻对碳纳米管场发射的影响.研究表明,接触电阻的存在,在高电场区域接触电阻抑制了碳纳米管的电子场发射,导致在高电场区域出现电流饱和及FN直线偏折现象.其原因可归结为接触电阻使得在碳纳米管顶端的局域电场相对于没有接触电阻时相对地减少. 关键词： 碳纳米管 场发射 接触电阻 电流饱和     

Adiabatic charge pumping in carbon nanotube quantum dots

We investigate charge pumping in carbon nanotube quantum dots driven by the electric field of a surface acoustic wave. We find that, at small driving amplitudes, the pumped current reverses polarity as the conductance is tuned through a Coulomb blockade peak using a gate electrode. We study the behavior as a function of wave amplitude, frequency, and direction and develop a model in which our results can be understood as resulting from adiabatic charge redistribution between the leads and quantum dots on the nanotube.     

Interaction of two charged media in the theory of a self-consistent field

In the framework of the Maxwell-Lorentz field theory a particular case is studied where two particles interact whose charge-to-mass ratios are different. A uniform nonlinear field equation is obtained. A set of simple partial particle-loke solutions is obtained.     

Aspects of Green's function methods versus self-consistent field theory

The basic methods of solving fully symmetric, nonlinear theories are stated. These are discussed in terms of Green's function methods and self-consistent field theory methods. The equivalence of many-body theory based on Green's functions with quantum field theory, on which the self-consistent field theory is based, is reviewed. A number of similarities, differences, and cautions involved with these methods are determined. In particular, since very often both methods are based upon use of the adiabatic theorem, which is typicallynot applicable to the models under consideration, a deviation in the self-consistent theory is discussed that avoids this problem. A similar idea is used for solution of models with the functional integral method. Ferromagnetic models are used at various places in illustrating some of the ideas. By contrasting these methods further insight may be gained into solving nonlinear, physical theories.