关于Semigroups of Linear Operators and Applications to Partial Differential Equations的两个注解

The Theory of Matrices. By F R. Gantmacher. Two volumes, pp. 374 and 276. 1959. (Translated from the Russian by K. A. Hirsch; Chelsea Publishing Company, New York)

Independent Component Analysis.

Initial-value ordinary differential equation solution via variable order Adams method (SIVA/DIVA) package is collection of subroutines for solution of nonstiff ordinary differential equations. There are versions for single-precision and double-precision arithmetic. Requires fewer evaluations of derivatives than other variable-order Adams predictor/ corrector methods. Option for direct integration of second-order equations makes integration of trajectory problems significantly more efficient. Written in FORTRAN 77.

Solving Ordinary Differential Equations

This paper gives a review of integration algorithms for finite dimensional mechanical systems that are based on discrete variational principles. The variational technique gives a unified treatment of many symplectic schemes, including those of higher order, as well as a natural treatment of the discrete Noether theorem. The approach also allows us to include forces, dissipation and constraints in a natural way. Amongst the many specific schemes treated as examples, the Verlet, SHAKE, RATTLE, Newmark, and the symplectic partitioned Runge–Kutta schemes are presented.

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Discrete mechanics and variational integrators

Hamiltonian Systems. Examples of Hamiltonian Systems. Symplecticness. The solution operator. Preservation of area. Checking preservation of area: Jacobians. Checking preservation of area: differential forms. Symplectic transformations. Conservation of volume. Numerical Methods. Numerical integrators. Stiff problems. Runge-Kutta methods. Partitioned Runge-Kutta methods. Runge-Kutta-Nystrom methods. Composition of methods - adjoints. Order conditions. Order conditions for Runge-Kutta methods. The local error in Runge-Kutta methods. Order conditions for PRK methods. The local error in Partitioned Runge-Kutta methods. Order conditions for Runge-Kutta-Nystrom methods. The local error in Runge-Kutta-Nystrom mehthods. Implementation. Variable step sizes. Embedded pairs. Numerical experience with variable step sizes. Implementing implicit methods. Fourth-order Gauss method. Symplectic integration. Symplectic methods. Symplectic Runge-Kutta methods. Symplectic partitioned Runge-Kutta methods. Symplectic Runge-Kutta-Nystrom methods. Necessity of the symplecticness conditions. Symplectic order conditions. Prelimiaries. Order conditions for symplectic RK methods. Order conditions for symplectic PRK methods. Order conditions for symplectic RKN methods. Homogenous form of the order conditions. Available symplectic methods. Symplecticness of the Gauss methods. Diagonally implicity Runge-Kutta methods. Other symplectic Runge-Kutta methods. Explicit partitioned Runge-Kutta methods. Available symplectic Runge-Kutta-Nystrom methods. Numerical experiments. A comparison of symplectic integrators. Variable step sizes for symplectic methods. Conclusions and recommendations. Properties of symplectic integrators. Backward error interpretation. An alternative approach. Conservation of energy. KAM theory. Generating functions. The concept of generating function. Hamilton-Jacobi equations. Integrators based on generating functions. Generating functions for RK methods. Canonical order theory. Lie formalism. The Poisson bracket. Lie operators and Lie series. The Baker-Campbell-Hausdorff formula. Application to fractional-step methods. Extension to the non-Hamilton case. High-order methods. High-order Lie methods. High-order Runge-Kutta-Nystrom methods. A comparison of order 8 symplectic integrators. Extensions. Partitioned Runge-Kutta methods for nonseparable Hamiltonian systems. Canonical B-series. Conjugate symplectic methods. Trapezoidal rule. Constrained systems. General Poisson structures. Multistep methods. Partial differential equations. Reversable systems. Volume preserving flows.

Numerical Hamiltonian Problems

The authors develop and test variable step symplectic Runge–Kutta–Nystrom algorithms for the integration of Hamiltonian systems of ordinary differential equations. Numerical experiments suggest that, for symplectic formulae, moving from constant to variable stepsizes results in a marked decrease in efficiency. On the other hand, symplectic formulae with constant stepsizes may outperform available standard (nonsymplectic) variable-step codes. For the model situation consisting in the long-time integration of the two-body problem, our experimental findings are backed by theoretical analysis.

The development of variable-step symplectic integrators with application to the two-body problem

Linearly implicit Runge—Kutta methods for advection—reaction—diffusion equations

In this paper we are concerned with the problem of solving numerically isospectral flows. These flows are characterized by the differential equation L' = [B(L), L]; L(0) = L 0 , where L 0 is a d x d symmetric matrix, B(L) is a skew-symmetric matrix function of L and [B, L] is the Lie bracket operator. We show that standard Runge-Kutta schemes fail in recovering the main qualitative feature of these flows, that is isospectrality, since they cannot recover arbitrary cubic conservation laws. This failure motivates us to introduce an alternative approach and establish a framework for generation of isospectral methods of arbitrarily high order.

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Numerical solution of isospectral flows

A class of explicit multistep exponential methods for abstract semilinear equations is introduced and analyzed. It is shown that the k-step method achieves order k, for appropriate starting values, which can be computed by auxiliary routines or by one strategy proposed in the paper. Together with some implementation issues, numerical illustrations are also provided.

M. P. Calvo

Papers

Numerical Hamiltonian Problems

The development of variable-step symplectic integrators with application to the two-body problem

Linearly implicit Runge—Kutta methods for advection—reaction—diffusion equations

Numerical solution of isospectral flows

A class of explicit multistep exponential integrators for semilinear problems