SMALL PERTURBATIONS OF A DISCRETE TWIST MAP

We investigate numerically a one-parameter family of twist mappings ac ting on a discrete lattice on the two-dimensional torus, and subject t o a perturbation whose magnitude has the same size as the lattice spac ing. These maps mimic the effects of (invertible) round-off errors on the orbits of an integrable twist map. We explore resonant and non-res onant behaviour in the limit of small lattice spacing, and find a dyna mics rich in arithmetical and statistical features. (C) Elsevier, Pari s.