Important aspects of geometric numerical integration
Ernst Hairer
Abstract.
At the example of Hamiltonian differential equations,
geometric properties
of the flow
are discussed that are only preserved by
special numerical integrators (such as symplectic and/or symmetric
methods). In the `non-stiff' situation the long-time
behaviour of these methods is well-understood
and can be explained with the help of a backward error analysis.
In the highly oscillatory (`stiff') case this theory
breaks down. Using a modulated Fourier expansion, much insight
can be gained for methods applied to problems where the high
oscillations stem from a linear part of the vector field and where
only one (or a few) high frequencies are present. This paper
terminates with numerical experiments at space
discretizations of the sine-Gordon equation, where a whole spectrum
of frequencies is present.
Key Words.
geometric numerical integration, Hamiltonian systems,
reversible differential
equations, backward error analysis, energy conservation,
modulated Fourier expansion, adiabatic invariants,
sine-Gordon equation.