Effects of Mass Discontinuity on the Numerical Solutions to Quantum Wells Using the Effective Mass Equation

This paper investigates the effects of mass dicontinuity on the numerical solutions to quantum wells using the effective mass equation. The numerical methods utilized are the finite element method with first-order elements, and the finite difference method with the entire truncated solution domain discretized by equally spaced nodes. The three Hamiltonians explored are the convention Hamiltonian, the BenDaniel and Duke Hamiltonian, and the Bastard Hamiltonian. It is shown that the proper discretization patterns for both numerical schemes may drastically improve the solution accuracy. The finite difference representation of the BenDaniel and Duke Hamiltonian using the direct mass average is found more accurate than the one using the harmonic mass average. It is further pointed out that, at the mass profile discontinuities, the commonly accepted interface conditions for the Bastard Hamiltonian are not natural conditions. This observation is critical if the Bastard Hamiltonian is to be solved numerically.     

Pairing-plus-quadrupole-plus-octupole model

The octupole-octupole interaction has been added to the old pairing-plus-quadrupole model. Symmetries of the HF mean field are discussed. It is shown that under the assumption of the S-symmetry of the HF mean field, only two quadrupole and two octupole parameters have non-zero expectation values in HFB ground state. A detailed analysis of two possible approaches to the HFB treatment of the model Hamiltonian is presented.We would like to thank Prof. J. de Boer for useful comments. This work was supported by DFG Bo 1109/1 and Volkswagen Foundation.     

Convergence criteria for the Hartree iterative solution of the general self-consistent field equations

The traditional Hartree method of solving the Hartree-Fock equations, by repeated diagonalization and recalculation of the single-particle Hamiltonian, is expressed in terms of repeated unitary transformations and shown to be applicable to the general SCF (self-consistent field) equations. The necessary and sufficient conditions for convergence to a unique local SCF solution are derived and it is shown that only a small class of solutions are obtainable by this method.     

The FBCS model and the inverse gap equations applied to the tin isotopes

The FBCS model for odd nuclei and the inverse gap equations are applied to a whole sequence of tin isotopes,viz.^111–125Sn. From spectroscopic data on the odd isotopes, the single-particle energies and interaction strengths are obtained. With these parameters the lowest states of the even isotopes are calculated by a number-projected two-quasiparticle diagonalization and by the usual BCS one. This is done with two Gaussian interactions and the SDI. In the case of the Gaussian forces the experimental energies are well reproduced by the number-projected treatment. Effective charges for Eλ transitions, which are required to reproduce the experimental transition rates, are rather constant for the whole series of isotopes, in case of the number-projected treatment. In addition a number of spectroscopic factors for one-nucleon transfer reactions are calculated and good agreement with experiments is observed.     

Determination of the Electromagnetic Lagrangian from a System of Poisson Brackets

The Lagrangian and Hamiltonian formulations of electromagnetism are reviewed and the Maxwell equations are obtained from the Hamiltonian for a system of many electric charges. It is shown that three of the equations which were obtained from the Hamiltonian, namely the Lorentz force law and two Maxwell equations, can be obtained as well from a set of postulated Poisson brackets. It is shown how the results derived from these brackets can be used to reconstruct the original Lagrangian for the theory aided by some reasoning based on physical concepts.     

THE SELF-CONSISTENT FIELD EQUATIONS AT FINITE NUCLEAR TEMPERATURE——THE GENERALIZED HFB EQUATIONS

In order to study the variation of shell effects as well as pairing effects with nuclear temperature, we have extended the work of Sano and Yamasaki to generalize the HFB equations to finite nuclear temperature with the help of variational principle. When nullear temperature θ→0, sulh generalized HFB equations reduce to the conventional HFB equations. While the fermi gas model results can be obtained in the high temperature limit.     

System of differential equations in the momentum space for a three-body problem

A form of three-boson Skornyakov-Ter-Martirosyan equations differential in the momentum space is proposed. This form makes it possible to directly use the Danilov condition for self-adjointness of the three-particle Hamiltonian with zero-range pair interactions. The numerical solution for the system of differential equations of the Heun class is compared with the solutions for the Faddeev equations for the problem of determining the helium trimer spectrum.     

Bubble interaction dynamics in Lagrangian and Hamiltonian mechanics

Two models of interacting bubble dynamics are presented, a coupled system of second-order differential equations based on Lagrangian mechanics, and a first-order system based on Hamiltonian mechanics. Both account for pulsation and translation of an arbitrary number of spherical bubbles. For large numbers of interacting bubbles, numerical solution of the Hamiltonian equations provides greater stability. The presence of external acoustic sources is taken into account explicitly in the derivation of both sets of equations. In addition to the acoustic pressure and its gradient, it is found that the particle velocity associated with external sources appears in the dynamical equations.     

大气动力学方程的Hamilton算法

将大气动力学方程组写成正则算子方程的形式,通过引入泊松括号,并利用原方程组的无穷个不变量,深入研究其Hamilton性质,在忽略摩擦和外源强迫的情况下,证明了大气动力体系是一个Hamilton系统,从而构造出求解它的辛算法,并用数值试验检验了该算法.     

Hamiltonian approach to the dynamics of a chemostat

Based on the Hamiltonian approach to an analysis of the system of Monod equations describing the chemostat dynamics, their partial analytical solution is found for a certain class of initial conditions. It is shown that this class of initial conditions can be easily realized in microbiological practice, and the solution obtained is generally described by the attractor of the system trajectories. A methodical approach, which allows the given Hamiltonian formalism to be used to analyze the kinetics of growth of microorganisms in the chemostat, is developed and experimentally checked. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 46–53, July, 2000.     

Extraction of the spurious states from the solution of the motion equation within the random phase approximation

The general form of nuclear Hamiltonian equation of motion is derived within the Random Phase Approximation (RPA). The connection between the Goldstone modes of motion (spurious states) and the equations of motion is shown. The general method of extraction of spurious states from the solution of the RPA equations of motion is proposed.     

The quantum-fluctuations of the optical parametric oscillator. II

We set up an effective Hamiltonian for an optical parametric oscillator. It contains the Bose operators of the three modes, signal, idler, and pump and their coupling to heat baths. This Hamiltonian is shown to be equivalent to a set of equations of motion, derived in a previous paper (I) from a microscopically exact Hamiltonian, provided that the heat baths are chosen in an adequate way. The comparison with the laser Hamiltonian makes clear the close analogy of the underlying elementary processes of spontaneous emission from atoms and spontaneous parametric emission from light modes in nonlinear media. The Hamiltonian is used to derive a master equation for the statistical operator of the three-mode system. In the coherent state representation this master equation transforms into an equivalentc-number Fokker-Planck equation without any approximation. The solution is obtained below threshold by linearization and above threshold by quasilinearization of the nonlinear dissipation coefficients. The results agree with those which were obtained by quantum mechanical Langevin methods in a previous paper (I).     

Concerning the full integrability of hamiltonian equations of charged particle motion in a weakly inhomogeneous magnetic field

The Hamiltonian of a charged particle in a weakly inhomogeneous magnetic field is calculated up to terms on the order of a small parameter. Fast phase-averaged equations of motion are derived. It is shown that these equations are intergrable in quadratures. Thus, the problem of particle motion in a weakly inhomogeneous field is solved in the first-order approximation. To calculate the Hamiltonian, the coordinates related to the field are used. Then, the canonical change of variables is done with the help of the generating function; in the case of a homogeneous field, this results in the action-angle variables. Such a procedure has been already used in [1]. However, the small parameter was not explicitly introduced and final expressions for small and large parts of the Hamiltonian were not calculated in that paper. It is shown that the small part of the Hamiltonian is a trigonometric polynomial of the fast phase (this can be important when analyzing the influence of additional perturbations). Besides, the averaged equations appear to be treatable and can be integrated in quadratures.     

Spectrum of certain non-self-adjoint operators and solutions of Langevin equations with complex drift

As part of a program to evaluate expectations in complex distributions by longterm averages of solutions to Langevin equations with complex dirft, a simple one-dimensional example is examined in some detail. The validity and rate of convergence of this scheme depends on the spectrum of an associated non-selfadjoint Hamiltonian which is found numerically. In the regime where the stochastic evaluation should be accurate numerical solution of the Langevin equation shows this to be the case.     

A Note on the Equivalence of Post-Newtonian Lagrangian and Hamiltonian Formulations

Recently,it has been generally claimed that a low order post-Newtonian(PN)Lagrangian formulation,whose Euler-Lagrange equations are up to an infinite PN order,can be identical to a PN Hamiltonian formulation at the infinite order from a theoretical point of view.In general,this result is difficult to check because the detailed expressions of the Euler-Lagrange equations and the equivalent Hamiltonian at the infinite order are clearly unknown.However,there is no difficulty in some cases.In fact,this claim is shown analytically by means of a special first-order post-Newtonian(1PN)Lagrangian formulation of relativistic circular restricted three-body problem,where both the Euler-Lagrange equations and the equivalent Hamiltonian are not only expanded to all PN orders,but have converged functions.It is also shown numerically that both the Euler-Lagrange equations of the low order Lagrangian and the Hamiltonian are equivalent only at high enough finite orders.     

Why solve the Hamiltonian constraint in numerical relativity?

The indefinite sign of the Hamiltonian constraint means that solutions to Einstein's equations must achieve a delicate balance – often among numerically large terms that nearly cancel. If numerical errors cause a violation of the Hamiltonian constraint, the failure of the delicate balance could lead to qualitatively wrong behavior rather than just decreased accuracy. This issue is different from instabilities caused by constraint-violating modes. Examples of stable numerical simulations of collapsing cosmological spacetimes exhibiting local mixmaster dynamics with and without Hamiltonian constraint enforcement are presented.     

An approximation for rotation-projected expectation values of the energy for deformed nuclei and a derivation of the cranking variational equation

An approximation is given for the expectation value of the Hamiltonian with functions: where ¦?〉 is a HFB wave function of a deformed nucleus. This is achieved by expanding the overlap function of the energy 〈?¦ HD(Ω)¦?〉 in derivatives of the overlap function of the norm 〈? D(Ω)¦?〉. The cranking equations for even nuclei are yielded by varying the approximate energy.     

The ADM Hamiltonian at the postlinear approximation

The ADM Hamiltonian for a many-particle system is calculated up to the postlinear approximation, i.e., to the approximation that both the equations of motion for the particles and the equations of motion for the gravitational field in case of no-incoming radiation correctly result up to the postlinear approximation. The relation of this Hamiltonian to the ADM Hamiltonian obtained by a post-Newtonian approximation scheme which was applied up to the first radiation-reaction and radiation levels is discussed. From here the standard formulas for the mechanical angular momentum and energy losses as well as the radiated energy and angular momentum are deduced. Background logarithmic and logarithmic radiative terms are shown to be not present at our approximation if the condition of no-incoming radiation is fulfilled.     

Continuous canonical transformation for the double exchange model

The method of continuous canonical transformation is applied to the double exchange model with a purpose to eliminate the interaction term responsible for non conservation of magnon number. Set of differential equations for the effective Hamiltonian parameters is derived. Within the lowest order (approximate) solution we reproduce results of the standard (single step) canonical transformation. Results of the selfconsistent numerical treatment are compared with the other known studies for this model.