Window scaling in one-dimensional maps

We describe both the internal structure and the width of the periodic windows in one-dimensional maps, by considering a universal local submap. Both features are found to depend only on the order of the extremum of this submap. Moreover, we discuss how the windows are grouped in accumulating families, and we calculate the scaling of the widths within these families

The squeeze effect in non-integrable Hamiltonian systems

In non-integrable Hamiltonian systems (represented by mappings of the plane) the stable island around an elliptic fixed point is generally squeezed into the fixed point by three saddle points, when the rotation number ρ of the motion at the fixed point approaches 1/3. At ρ=1/3 the island is reduced to one single point.\ud A detailed investigation of this squeeze effect, and some of its global implications, is presented by means of a typical two-dimensional area-preserving map. In particular, it turns out that the squeeze effect occurs in any mapping for which the Taylor expansion around the fixed point contains a quadratic term, whereas it does not occur if the first non-linear term is cubic. We illustrate this with two physical examples: a compass needle in an oscillating field, showing the squeeze effect, and a ball which bounces on a vibrating plane, for which the squeeze effect does not occur

Bifurcations in two-dimensional reversible maps

We give a treatment of the non-resonant bifurcations involving asymmetric fixed points with Jacobian J≠1 in reversible mappings of the plane. These bifurcations include the saddle-node bifurcation not in the neighbourhood of a fixed point with J≠1, as well as the so-called transcritical bifurcations and generalized Rimmer bifurcations taking place at a fixed point with Jacobian J≠1. The bifurcations are illustrated by some simple examples of model maps. The Rimmer type of bifurcation, with e.g. a center point with J≠1 changing into a saddle with Jacobian J≠1, an attractor and a repeller, occurs under more general conditions, i.e. also in non-reversible mappings if only a certain order of local reversibility is satisfied. These Rimmer bifurcations are important in connection with the emergence of dissipative features in non-measure-preserving reversible dynamical systems

Phase-length distributions in intermittent band switching

The distribution of phase lengths t for intermittent band switching is investigated. Its form is observed to deviate from a exponential function; a minimal phase length is seen to exist and the probabilities for the first few occuring phase lengths are often strongly enhanced or suppressed. These deviations are analyzed and described explicitly in terms of the parameters of a model map

Short-phase anomalies in intermittent band switching

The distribution of phase lengths t for intermittent band switching is investigated for small t. Some typical deviations from exponential behaviour are reported, in particular the occurrence of a minimal phase length with enhanced probability

The birth of twin Poincaré-Birkhoff chains near 1:3 resonance

For a typical area-preserving map we describe the birth process of two twin Poincaré-Birkhoff chains, i.e. two rings consisting of center points alternated by saddles, wound around an elliptic fixed point. These twin chains are not born out of the elliptic fixed point, but in the plane, from an annular region where the rotation number has a rational extremum. This situation generically occurs near a 1:3 resonance. We find that the birth of two twin PB chains in such an annular region requires first the birth of two “dimerized” chains of saddle-center pairs, by a tangent bifurcation. The transition from two dimerized chains to two PB chains involves the breakup of homoclinic saddle connections and the formation of heteroclinic connections; it amounts to the reconnection phenomenon of Howard and Hohs.\ud \ud Our results can be regarded as a supplement to the Poincaré-Birkhoff theorem, for the case that the twist condition is not satisfied

Eine neue Ancylopteryx-Art aus Liberia

Unter den von Dr. J. Büttikofer auf seiner Liberiareise im Jahre 1880 erbeuteten Neuropteren findet sich eine neue Ancylopteryx-Art, welche sich auf den ersten Blick von der von Gerstaecker aus Kamerun beschriebenen, verwandten A. splendidissima, durch ihre beträchtlichere Grösse, die milchig getrübten, nur wenig schillernden, mit 2 punktförmigen schwarzbraunen Flecken versehenen, Vorderflügel unterscheidet. Ausserdem ist noch eine dritte Art dieser Gattung, A. venusta Hagen aus Mossambique, bekannt, so dass wir also nun 3 Arten dieser Gattung aus Afrika kennen. Die neue Art charakterisirt sich folgendermassen: Kopf, Thorax und Abdomen gelb