Two-center problem for the dirac equation

The ground-state wave function and the energy term of a relativistic electron moving in the field of two fixed Coulomb centers are calculated analytically by the LCAO method. The resulting analytic formula is used to calculate the critical internuclear distance at which the energy term crosses the boundary of the lower continuum.     

Minimization methods for the one-particle dirac equation

Taking into account relativistic effects in quantum chemistry is crucial for accurate computations involving heavy atoms. Standard numerical methods can deal with the problem of variational collapse and the appearance of spurious roots only in special cases. The goal of this Letter is to provide a general and robust method to compute particle bound states of the Dirac equation.     

Gauge invariance and the dirac equation

The gauge invariance of the Dirac equation is reviewed and gauge-invariant operators are defined. The Hamiltonian is shown to be gauge dependent, and an energy operator is defined which is gauge invariant. Gauge-invariant operators corresponding to observables are shown to satisfy generalized Ehrenfest theorems. The time rate of change of the expectation value of the energy operator is equal to the expectation value of the power operator. The virial theorem is proved for a relativistic electron in a time-varying electromagnetic field. The conventional approach to probability amplitudes, using the eigenstates of the unperturbed Hamiltonian, is shown in general to be gauge dependent. A gaugeinvariant procedure for probability amplitudes is given, in which eigenstates of the energy operator are used. The two methods are compared by applying them to an electron in a zero electromagnetic field in an arbitrary gauge. Presented at the Dirac Symposium, Loyola University, New Orleans, May 1981.     

A relation between the dirac field of the electron and electromagnetic fields

There is a point of view from which a field governed by the Dirac equation for the electron is the same as a field governed by the Maxwell-Lorentz equations for electromagnetic fields. This observation suggests the possibility that the two sets of equations are of the same origin.     

Supercriticality and transmission resonances in the dirac equation

It is shown that a Dirac particle of mass m and arbitrarily small momentum will tunnel without reflection through a potential barrier V = U(c)(x) of finite range provided that the potential well V = -U(c)(x) supports a bound state of energy E = -m. This is called a supercritical potential well.     

Energy spectrum of the dirac equation for the Scharzschild and Kerr fields

We consider the effect of relativistic corrections and rotation of the central body on the structure of the energy spectrum of a particle with spin in the Schwarzchild and Kerr fields. A splitting of levels is obtained, which corresponds to the classical shift of the perihelion of the orbit and precession of the plane of the gravitational spin-orbit interaction and several nonlinear spin effects are calculated.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 86–92, February, 1988.     

New exact solutions of the dirac equation. XII

The search for exact solutions of the Dirac equation begun in [1] is continued. We find three new types of external electromagnetic fields where the Dirac equation, Klein-Gordon equation, and classical Lorentz equation can be solved exactly. We find fields for which explicit solutions to the Klein-Gordon equation can be found but for which explicit solutions of the Dirac equation cannot.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 81–86, January, 1985.     

New exact solutions of the dirac equation. I

Three new types of external electromagnetic fields, allowing exact solution of the Dirac and Klein-Gordon equations, are found in this paper. The wave functions are expressed in terms of quadratures. Solutions of the corresponding classical relativistic equations of motion are also found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 7, pp. 95–101, July, 1973.     

Dual kinetic balance approach to basis-set expansions for the dirac equation

A new approach to finite basis sets for the Dirac equation is developed. It does not involve spurious states and improves the convergence properties of basis-set calculations. Efficiency of the method is demonstrated for finite basis sets constructed from B splines by calculating the one-loop self-energy correction for a hydrogenlike ion.     

A simple analytic solution of the dirac equation with a scalar linear potential

We give a simple, approximate analytic solution of the massless Dirac equation with a scalar linear potential. Its accuracy is better than 99% for the energy eigenvalues. We also discuss the effect of the centre-of-mass correction as well as the spin-orbit splitting with the help of the analytic solution.     

The dirac equation in 5-dimensional Wesson gravity

Using the Ma interpretation of 5D Wesson gravity, we construct the corresponding Weyl equation in a quasistatic spherically symmetric gravitational background in order to look at the mass term predicted by the theory. We find that the value of this mass depends strongly on the boundary conditions selected for theg55. As an example we calculate its value at the surface of the earth.     

Approximate scattering solutions of the dirac equation for electron-nucleus processes in light nuclei

Scattering solutions of the second-order Dirac equation for the case of the Coulomb potential and which are correct to first order in the coupling constantZe ²/hc are investigated and found to describe pure Coulomb scattering equally well as the Sommerfeld-Maue wave functions. Errors introduced by the use of these solutions are studied in a numerical calculation of cross sections for nuclear electric-quadrupole excitation by high-energy electrons. The use of these wave functions is suggested for simplified calculations of lowest-order Coulomb corrections to Born approximation results for various electron-nucleus processes.     

Spurious states of the dirac equation in a finite basis set

The occurrence of spurious states for the Dirac equation in a finite basis set is considered. For a Coulomb central-field potential, the spectra of the radial Dirac operator in a finite basis set (without using the kinetic balance) are shown to coincide for two different values of the relativistic quantum number κ that differ in sign. For an attractive Coulomb potential, this means that, for any basis set, spurious states p _1/2, d _3/2, … (κ > 0) arise, whose energies exactly coincide with energies of the states 1s _1/2, 2p _3/2, … (κ < 0), respectively. In addition, the negative spectra of the Dirac operator in a finite basis set for κ > 0 and κ < 0 also coincide.     

Dirac方程的数值解法及其在原子总能量计算中的应用

中心势近似下径向Dirac方程的求解是相对论性原子(离子)结构计算的基础.本文通过相对论性方程中径向波函数大分量与非相对论方程径向波函数的类比,提出了径向Dirac方程的一种数值解法.为了验证数值解法的精度和可靠性,首先将数值结果与类氢势作用下的解析解进行比较.然后,将这种算法扩展到基于解析势的相对论性原子结构计算中,并将计算出的总能量与实验结果和其他方法得到的结果进行对比.     

Solution of dirac equation in a singularity-free Kaluza-Klein cosmological model

The singularity-free solution of (4 + D) -dimensional Einstein field equations for the Kaluza-Klein cosmological model is obtained. Then the Dirac equations are solved in this model.     

On the total bandwidth for the rational Harper's equation

In the last years several contributions have been done around the total bandwidth of the spectrum for the Harper's operator. In particular an interesting conjecture has been proposed by Thouless which gives also strong convincing arguments for the proof in special cases. On the other hand, in the study of the Cantor structure of the spectrum, B. Helffer and J. Sjöstrand have justified an heuristic semiclassical approach proposed by M. Wilkinson. The aim of this article is to explain how one can use the first step of this approach to give a rigorous semi-classical proof of the Thouless formula in some of the simplest cases. We shall also indicate how one can hope with more effort to prove rigorously recent results of Last and Wilkinson on the same conjecture.     

An interpretation of the energy-momentum tensor of the dirac field with anomalous magnetic moment

The ground state radiative widths of the 1.56 MeV (3/2⁺) and the 1.35 MeV (5/2^?) levels in¹⁹F were determined by inelastic electron scattering. The measured cross sections have been analysed using DWBA calculations. The resultsΓ _y ⁰ (5/2^?→1/2^?,E3)=(8.1±1.7)·10^?10eV andΓ _y ⁰ (3/2⁺→1/2⁺,E2=(1.76±0.15)·10^?4eV are in agreement with, but more accurate than, former measurements.