Some comments on numerical methods for chaos problems

Hamiltonian systems with chaotic regions are particularly slippery to treat numerically. Numerical treatments can introduce nonphysical features. Simple examples illustrate some of the pitfalls. Integer, or discrete, arithmetic is a favorite ''workaround.'' While it does not cure chaos, it clarifies the interaction of computational methods with the underlying mathematical structure. Be forewarned: I won't give any prescription that is guaranteed to give a good and reliable method to handle chaotic problems numerically. Instead, I'll stress a few of the concerns and describe one or two pitfalls.