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1.
We study theoretically the level shift of the Dirac oscillator perturbed by any sharply peaked potential approaching a surface delta potential. A Green function method is used to obtain closed expressions for all partial waves and parities. 相似文献
2.
C. -S. Jia P. Guo Y. -F. Diao L. -Z. Yi X. -J. Xie 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):41-48
By using the basic concepts of the supersymmetric quantum mechanics formalism and the function analysis method, we solve the
Dirac equation with vector and scalar potentials and obtain the bound-state solutions for the nuclei in the relativistic P?schl-Teller
potential. All of the analyses are prepared under the conditions of the exact spin symmetry and pseudospin symmetry. The exact
energy equation and corresponding two-component spinor wave functions for s -wave bound states are obtained analytically. 相似文献
3.
Tunneling of Dirac fermions in graphene through a velocity barrier with modulated by magnetic fields
Jian-Hui Yuan Jian-Jun ZhangQi-Jun Zeng Jun-Pei ZhangZe Cheng 《Physica B: Condensed Matter》2011,406(22):4214-4220
We study magnetic field modulated transport properties of Dirac fermions in graphene, where Dirac fermions penetrate through a velocity barrier. We find strong wave vector filtering and resonant effect. The angular-dependent region of resonant tunneling is suppressed by tuning velocity barriers. We can also found that the confined states in this velocity barrier can be changed by the magnetic field. Various novel devices, such as wavevector filter and magnetic switches, may be constructed based on our observed phenomena. 相似文献
4.
The Dirac equation in a curved spacetime depends on a field of coefficients (essentially the Dirac matrices), for which a continuum of different choices are possible. We study the conditions under which a change of the coefficient fields leads to an equivalent Hamiltonian operator H, or to an equivalent energy operator E. We do that for the standard version of the gravitational Dirac equation, and for two alternative equations based on the tensor representation of the Dirac fields. The latter equations may be defined when the spacetime is four‐dimensional, noncompact, and admits a spinor structure. We find that, for each among the three versions of the equation, the vast majority of the possible coefficient changes do not lead to an equivalent operator H, nor to an equivalent operator E, whence a lack of uniqueness. In particular, we prove that the Dirac energy spectrum is not unique. This non‐uniqueness of the energy spectrum comes from an effect of the choice of coefficients, and applies in any given coordinates. 相似文献
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Wei-Ran Cao Yong-Long Wang Xiao-Lei Chen Hua Jiang Chang-Tan Xu Hong-Shi Zong 《Physics letters. A》2019,383(17):2124-2129
For an electron confined to a surface reconstructed by double-frequency corrugations, we give the effective Hamiltonian by the formula of geometric influences, obtain an additive scalar potential induced by curvature that consists of attractive wells with different depth. The difference is generated by the multiple frequency of the double-frequency corrugation. Subsequently, we investigate the effects of geometric potential on the transmission probability, and find the resonant tunneling peaks becoming rapidly sharper and the transmission gaps being substantially widened with increasing the multiple frequency. As a potential application, double-frequency corrugations can be employed to select electrons with particular incident energy, as an electronic switch, which are more effective than a single-frequency ones. 相似文献
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An optical method is presented which permits the determination of the free surface velocity of liquid films flowing on curved surfaces. The feasibility of this technique, which involves the laser tomography and photochromic dye activation techniques, is demonstrated on an oil film flowing around a finned tube. Results for different tube geometries and flow conditions are presented. Advantages and limits of the laser photochromic velocimetry technique are discussed. 相似文献
10.
We study the problem of a possible change in the number of constraints in linear relativistic wave equations (-iβ
μ
∂
μ
+m)ψ=0 for particles of unique mass, on introduction of minimal coupling to an external electromagnetic field. Complementing our
earlier work in which we obtained conditions for non-loss of constraints in equations characterised by the minimalβ-algebraβ
0
5 =β
0
3 we derive here the conditions for such theories not to generate more constraints than in the free case. The results are illustrated
by considering specific equations and a fallacy in certain conclusions of Kobayashi and Shamaly on this problem is pointed
out. 相似文献
11.
WANG Xiuming & ZHANG Hailan . CSIRO Petroleum ARRC PO BOX Technology Park Bentley WA Australia . Institute of Acoustics Chinese Academy of Sciences Beijing China . Present address: Institute of Acoustics Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2004,47(5):633-648
Modelling and understanding the effect of elastic wave propagation along a curved free surface has been one of the important issues in seismic exploration[1—3], earth seis-mology[4], and non-destructive ultrasonic detection[5]. Several approaches have beenproposed for simulating wave propagation in heterogeneous media with a topographic stress-release boundary. These include finite-element methods (FEM), boundary element methods (BEM), finite-difference methods (FDM), pseudo-spectral metho… 相似文献
12.
We demonstrate the nontrivial scaling behavior of Ising models defined on (i) a donut-shaped surface and (ii) a curved surface with a constant negative curvature. By performing Monte Carlo simulations, we find that the former model has two distinct critical temperatures at which both the specific heat C(T) and magnetic susceptibility χ(T) show sharp peaks. The critical exponents associated with the two critical temperatures are evaluated by the finite-size scaling analysis; the result reveals that the values of these exponents vary depending on the temperature range under consideration. In the case of the latter model, it is found that static and dynamic critical exponents deviate from those of the Ising model on a flat plane; this is a direct consequence of the constant negative curvature of the underlying surface. 相似文献
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M. Arminjon 《Annalen der Physik》2011,523(12):1008-1028
In a general spacetime, the possible choices for the field of orthonormal tetrads lead (in standard conditions) to equivalent Dirac equations. However, the Hamiltonian operator is got from rewriting the Dirac equation in a form adapted to a particular reference frame, or class of coordinate systems. That rewriting does not commute with changing the tetrad field (uα ). The data of a reference frame F fixes a four‐velocity field v, and also fixes a rotation‐rate field Ω . It is natural to impose that u0 = v. We show that then the spatial triad (up) can only be rotating w.r.t. F, and that the title problem is solved if one imposes that the corresponding rotation rate Ξ be equal to Ω – or also, if one imposes that Ξ = 0 . We also analyze other proposals which were aimed at solving the problem of the non‐uniqueness of the Dirac Hamiltonian. 相似文献
15.
The asymptotics as ɛ → 0 of the spectrum of the shifted Laplace operator H = ɛΔ + ∂v on a two-dimensional compact surface of revolution homeomorphic to the sphere is described, where v is a vector field. 相似文献
16.
K.-E. Thylwe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):591-596
The analysis of bound radial Dirac states is shown to simplify for problems with an equal mixture of Lorentz vector and Lorentz scalar potentials, thus satisfying a so-called spin symmetry of the energy spectrum. Typical relativistic restrictions on potentials that are singular at the origin then disappear.
Such potentials may even be strongly singular at the origin like the well known Lennard-Jones potentials modelling many atom-atom
interactions, and they reduce to non-relativistic potentials of identical form. Bound state energies for potentials with equal
vector- and scalar couplings are compared with those of a pure vector coupling of the same radial (attractive screened and
unscreened Coulomb) shapes, and with non-relativistic results. 相似文献
17.
In the present Letter, the multiple scattering theory (MST) for calculating the elastic wave band structure of two-dimensional phononic crystals (PCs) is extended to include the interface/surface stress effect at the nanoscale. The interface/surface elasticity theory is employed to describe the nonclassical boundary conditions at the interface/surface and the elastic Mie scattering matrix embodying the interface/surface stress effect is derived. Using this extended MST, the authors investigate the interface/surface stress effect on the elastic wave band structure of two-dimensional PCs, which is demonstrated to be significant when the characteristic size reduces to nanometers. 相似文献
18.
Effect of surface tension on the mode selection of vertically excited surface waves in a circular cylindrical vessel 下载免费PDF全文
Singular perturbation theory of two-time-scale expansions was developed in inviscid fluids to investigate patternforming, structure of the single surface standing wave, and its evolution with time in a circular cylindrical vessel subject to a vertical oscillation. A nonlinear slowly varying complex amplitude equation, which involves a cubic nonlinear term,an external excitation and the influence of surface tension, was derived from the potential flow equation. Surface tensionwas introduced by the boundary condition of the free surface in an ideal and incompressible fluid. The results show that when forced frequency is low, the effect of surface tension on the mode selection of surface waves is not important.However, when the forced frequency is high, the surface tension cannot be neglected. This manifests that the function of surface tension is to cause the free surface to return to its equilibrium configuration. In addition, the effect of surface tension seems to make the theoretical results much closer to experimental results. 相似文献
19.
The resonant absorption of a plasma surface wave is supposed to be an important and efficient mechanism of power deposition for a surface wave plasma source. In this paper, by using the particle-in-cell method and Monte Carlo simulation, the resonance absorption mechanism is investigated. Simulation results demonstrate the existence of surface wave resonance and show the high efficiency of heating electrons. The positions of resonant points, the resonance width and the spatio-temporal evolution of the resonant electric field are presented, which accord well with the theoretical results. The paper also discusses the effect of pressure on the resonance electric field and the plasma density. 相似文献
20.
The effect of the attractive well of the potential energy surface for Ne--HCl on rotationally inelastic partial wave cross sections 下载免费PDF全文
An interaction potential of the Ne-HC1 van der Waals complex is obtained by utilizing the Huxley analytic potential function to fit the accurate interaction energy data, which have been computed at the coupled cluster singles and doubles including connected triple excitations level and with the augmented correlation consistent polarized valence quintuple zeta basis set extended with a set of 3s3p2dlflg mid-bond functions [CCSD (T)/aug-cc-pV5Z-33211]. The close coupling calculation of state-to-state partial cross sections for collision of Ne with HC1 is first performed by employing the fitted interaction potential. This calculation is performed at the incident energies: 40, 60, 75 and 100 meV, separately. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic state-to-state partial cross sections are discussed in detail. Two maxima are present in the rotationally inelastic partial cross sections and they originate from different mechanisms.[第一段] 相似文献