约束Hamilton系统的Lie对称性及其在场论中的应用

研究了约束Hamilton系统的Lie对称性,得到了场论系统的守恒量.首先给出约束Hamilton系统的正则运动方程和固有约束方程;其次构建了约束Hamilton 系统的Lie对称性确定方程和结构方程;然后给出了约束Hamilton系统的Lie守恒定理和守恒量;最后研究了复标量场与Chern-Simons项耦合系统的Lie对称性和另外一个例子以说明此方法在场论中的应用.     

太阳帆塔轨道和姿态耦合动力学建模及辛求解

在建立太阳帆塔太阳能电站简化模型的基础上,将系统的动力学方程从Lagrange体系导入到了Hamilton体系,给出了带约束的Hamilton正则方程;进而采用祖冲之类算法和辛Runge-Kutta方法分析了太阳帆塔轨道和姿态耦合系统的动力学特性,并讨论了算法的保能量、保约束特性;最后,数值模拟了系统的动力学特性,说明了所提方法的有效性.     

吴消元法在Lagrange和Hamilton方程中的应用

主要借鉴吴消元法,研究带约束动力学中多项式类型Lagrange方程和Hamilton方程,提出了一种求约束的新算法．与以前算法相比,新算法无需求Hessian矩阵的秩,无需判定方程的线性相关性,从而大为减少了计算步骤,且计算更为简单．此外,计算过程中膨胀较小,且多数情形下无膨胀．利用符号计算软件,新算法可在计算机上实现．     

双参数弹性地基上正交各向异性矩形薄板自由振动问题的Hamilton方法

本文运用矩阵多元多项式的带余除法把双参数弹性地基上正交各向异性矩形薄板的振动方程转化为Hamilton系统,利用分离变量给出对应的Hamilton算子.通过计算得到对边简支问题所对应Hamilton算子的本征值和本征函数系,并证明了该本征函数系的辛正交性和在Cauchy主值意义下的完备性.根据本征函数系的完备性,得到对应Hamilton系统的通解,进而给出双参数弹性地基上正交各向异性矩形薄板对边简支振动问题振型函数的通解.此外,通过两个例子说明此方法可以计算出自由振动问题的频率和振型函数.     

一族新的可积系及其双约束流的Hamilton正则表示

基于一个新的等谱问题，按屠格式导出了一族新的可积系，具有双Hamilton结构，通过建立双对称约束，得到了该方程族的两组约束流，并将其化为正则的Hamilton系统。     

一类锥约束变分不等式问题的最优性条件

利用像空间分析法,本文研究了带锥约束的变分不等式的最优性条件.利用Gerstewitz非线性标量化函数,给出了三个非线性弱分离函数、两个非线性正则弱分离函数和一个非线性强分离函数.然后,利用此分离函数,得到了带锥约束的变分不等式的弱或强的最优性条件.     

用投影方法求耗散广义Hamilton约束系统的李群积分

针对耗散广义Hamilton约束系统,通过引入拉格朗日乘子和采用投影技术,给出了一种保持动力系统内在结构和约束不变性的李群积分法．首先将带约束条件的耗散Hamilton系统化为无约束广义Hamilton系统, 进而讨论了无约束广义Hamilton系统的李群积分法,最后给出了广义Hamilton约束系统李群积分的投影方法．采用投影技术保证了约束的不变性,引入拉格朗日乘子后,在向约束流形投影时不会破坏原动力系统的李群结构．讨论的内容仅限于完整约束系统, 通过数值例题说明了方法的有效性．     

带约束动力学辛算法的符号计算

首先对带约束动力学中的辛算法作了改进,利用吴消元法求解多项式类型Euler-Lagrange方程.在辛算法的基础上,根据线性方程组理论和相容条件提出了一个求解约束的新算法.新算法的推导过程比辛算法严格,而且计算也比辛算法简单,并且多项式类型的Euler-Lagrange仍可以用吴消元法求解.另外,对于某些非多项式类型的Euler-Lagrange方程,可以先化为多项式类型,再用吴消元法求解.利用符号计算软件,上述算法都可以在计算机上实现.     

非线性非完整系统Vacco动力学方程的积分方法*

本文给出积分非线性非完整系统Vacco动力学方程的积分方法.首先,将Vacco动力学方程表示为正则形式和场方程形式;然后,分别用梯度法,单分量法和场方法积分相应完整系统的动力学方程,并加上非完整约束对初条件的限制而得到非线性非完整系统Vacco动力学方程的解.     

超Broer-Kaup-Kupershmidt族的双非线性化

得出了超Broer-Kaup- Kupershmidt族Lax对的对称约束及其双非线性化.在得到的对称约束F,把超Broer- Kaup-Kupershmidt族的n阶流分解成定义在对应于动力变量x和tn的超对称流形上的两种超有限维可积Hamilton系统.此外,显式给出了Liouville可积性所需的运动积分.     

Binary nonlinearization of spectral problems of the perturbation AKNS systems

The method of nonlinearization of spectral problems is extended to the perturbation AKNS systems, and a new kind of finite-dimensional Hamiltonian systems is obtained. It is shown that the obtained Hamiltonian systems are just the perturbation systems of the well-known constrained AKNS flows and thus their Liouville integrability is established by restoring from the Liouville integrability of the constrained AKNS flows. As a byproduct, the process of binary nonlinearization of spectral problems and the process of perturbation of soliton equations commute in the case of the AKNS hierarchy.     

Construction of starting algorithms for the RK-Gauss methods

In this paper starting algorithms for the numerical solution of stage equations in Runge-Kutta-Gauss formulae with 2, 3 and 4 stages are constructed. For each of these formulae, three types of starting algorithms are given according to their requirement of none, one or two additional function evaluations per step. Numerical experiments with Hamiltonian systems are presented to show the superior performance of the new starting algorithms of high order.     

Global modified Hamiltonian for constrained symplectic integrators

Summary. We prove that the numerical solution of partitioned Runge-Kutta methods applied to constrained Hamiltonian systems (e.g., the Rattle algorithm or the Lobatto IIIA–IIIB pair) is formally equal to the exact solution of a constrained Hamiltonian system with a globally defined modified Hamiltonian. This property is essential for a better understanding of their longtime behaviour. As an illustration, the equations of motion of an unsymmetric top are solved using a parameterization with Euler parameters. Mathematics Subject Classification (2000):65L06, 65L80, 65P10     

Binary nonlinearization of AKNS spectral problem under higher-order symmetry constraints

Binary nonlinearization of AKNS spectral problem is extended to the cases of higher-order symmetry constraints. The Hamiltonian structures, Lax representations, r-matrices and integrals of motion in involution are explicitly proposed for the resulting constrained systems in the cases of the first four orders.The obtained integrals of motion are proved to be functionally independent and thus the constrained systems are completely integrable in the Liouville sense.     

Numerical integration of constrained Hamiltonian systems using Dirac brackets

We study the numerical properties of the equations of motion of constrained systems derived with Dirac brackets. This formulation is compared with one based on the extended Hamiltonian. As concrete examples, a pendulum in Cartesian coordinates and a chain molecule are treated.

     

Canonical transformations of the extended phase space and integrable systems

We investigate the explicit construction of a canonical transformation of the time variable and the Hamiltonian whereby a given completely integrable system is mapped into another integrable system. The change of time induces a transformation of the equations of motion and of their solutions, the integrals of motion, the methods of separation of variables, the Lax matrices, and the correspondingr-matrices. For several specific families of integrable systems (Toda chains, Holt systems, and Stäckel-type systems), we construct canonical transformations of time in the extended phase space that preserve the integrability property.     

Hamiltonian Systems near Relative Equilibria

We give explicit differential equations for the dynamics of Hamiltonian systems near relative equilibria. These split the dynamics into motion along the group orbit and motion inside a slice transversal to the group orbit. The form of the differential equations that is inherited from the symplectic structure and symmetry properties of the Hamiltonian system is analysed and the effects of time reversing symmetries are included. The results will be applicable to the stability and bifurcation theories of relative equilibria of Hamiltonian systems.     

Modelling of three-dimensional mechanical systems using point coordinates with a recursive approach

In this paper, the dynamic simulation of constrained mechanical systems that are interconnected of rigid bodies is studied using projection recursive algorithm. The method uses the concepts of linear and angular momentums to generate the rigid body equations of motion in terms of the Cartesian coordinates of a dynamically equivalent constrained system of particles, without introducing any rotational coordinates and the corresponding rotational transformation matrix. Closed-chain system is transformed to open-chain by cutting suitable kinematical joints and introducing cut-joint constraints. For the resulting open-chain system, the equations of motion are generated recursively along the serial chains. An example is chosen to demonstrate the generality and simplicity of the developed formulation.     

Nonlinearization of the Lax pairs for discrete Ablowitz-Ladik hierarchy

The discrete Ablowitz-Ladik hierarchy with four potentials and the Hamiltonian structures are derived. Under a constraint between the potentials and eigenfunctions, the nonlinearization of the Lax pairs associated with the discrete Ablowitz-Ladik hierarchy leads to a new symplectic map and a class of finite-dimensional Hamiltonian systems. The generating function of the integrals of motion is presented, by which the symplectic map and these finite-dimensional Hamiltonian systems are further proved to be completely integrable in the Liouville sense. Each member in the discrete Ablowitz-Ladik hierarchy is decomposed into a Hamiltonian system of ordinary differential equations plus the discrete flow generated by the symplectic map.