49,941 research outputs found
Exotic Baker and wandering domains for Ahlfors islands maps
Let X be a Riemann surface of genus at most 1, i.e. X is the Riemann sphere
or a torus. We construct a variety of examples of analytic functions g:W->X,
where W is an arbitrary subdomain of X, that satisfy Epstein's "Ahlfors islands
condition". In particular, we show that the accumulation set of any curve
tending to the boundary of W can be realized as the omega-limit set of a Baker
domain of such a function. As a corollary of our construction, we show that
there are entire functions with Baker domains in which the iterates converge to
infinity arbitrarily slowly. We also construct Ahlfors islands maps with
wandering domains and logarithmic singularities, as well as examples where X is
a compact hyperbolic surface.Comment: 18 page
On the Connectedness and Diameter of a Geometric Johnson Graph
Let be a set of points in general position in the plane. A subset
of is called an \emph{island} if there exists a convex set such that . In this paper we define the \emph{generalized island Johnson
graph} of as the graph whose vertex consists of all islands of of
cardinality , two of which are adjacent if their intersection consists of
exactly elements. We show that for large enough values of , this graph
is connected, and give upper and lower bounds on its diameter
No elliptic islands for the universal area-preserving map
A renormalization approach has been used in \cite{EKW1} and \cite{EKW2} to
prove the existence of a \textit{universal area-preserving map}, a map with
hyperbolic orbits of all binary periods. The existence of a horseshoe, with
positive Hausdorff dimension, in its domain was demonstrated in \cite{GJ1}. In
this paper the coexistence problem is studied, and a computer-aided proof is
given that no elliptic islands with period less than 20 exist in the domain. It
is also shown that less than 1.5% of the measure of the domain consists of
elliptic islands. This is proven by showing that the measure of initial
conditions that escape to infinity is at least 98.5% of the measure of the
domain, and we conjecture that the escaping set has full measure. This is
highly unexpected, since generically it is believed that for conservative
systems hyperbolicity and ellipticity coexist
Strictly Toral Dynamics
This article deals with nonwandering (e.g. area-preserving) homeomorphisms of
the torus which are homotopic to the identity and strictly
toral, in the sense that they exhibit dynamical properties that are not present
in homeomorphisms of the annulus or the plane. This includes all homeomorphisms
which have a rotation set with nonempty interior. We define two types of
points: inessential and essential. The set of inessential points is
shown to be a disjoint union of periodic topological disks ("elliptic
islands"), while the set of essential points is an essential
continuum, with typically rich dynamics (the "chaotic region"). This
generalizes and improves a similar description by J\"ager. The key result is
boundedness of these "elliptic islands", which allows, among other things, to
obtain sharp (uniform) bounds of the diffusion rates. We also show that the
dynamics in is as rich as in from the rotational
viewpoint, and we obtain results relating the existence of large invariant
topological disks to the abundance of fixed points.Comment: Incorporates suggestions and corrections by the referees. To appear
in Inv. Mat
Action-gradient-minimizing pseudo-orbits and almost-invariant tori
Transport in near-integrable, but partially chaotic,
degree-of-freedom Hamiltonian systems is blocked by invariant tori and is
reduced at \emph{almost}-invariant tori, both associated with the invariant
tori of a neighboring integrable system. "Almost invariant" tori with rational
rotation number can be defined using continuous families of periodic
\emph{pseudo-orbits} to foliate the surfaces, while irrational-rotation-number
tori can be defined by nesting with sequences of such rational tori. Three
definitions of "pseudo-orbit," \emph{action-gradient--minimizing} (AGMin),
\emph{quadratic-flux-minimizing} (QFMin) and \emph{ghost} orbits, based on
variants of Hamilton's Principle, use different strategies to extremize the
action as closely as possible. Equivalent Lagrangian (configuration-space
action) and Hamiltonian (phase-space action) formulations, and a new approach
to visualizing action-minimizing and minimax orbits based on AGMin
pseudo-orbits, are presented.Comment: Accepted for publication in a special issue of Communications in
Nonlinear Science and Numerical Simulation (CNSNS) entitled "The mathematical
structure of fluids and plasmas : a volume dedicated to the 60th birthday of
Phil Morrison
A computer-assisted proof of symbolic dynamics in Hyperion's inner rotation model
The rotation of Hyperion is often modelled by equations of motion of an
ellipsoidal satellite. The model is expected to be chaotic for large range of
parameters. The paper contains a rigorous computer-assisted proof of the
existence of symbolic dynamics in its dynamics by the use of CAPD C++ library.Comment: 14 pages, 11 figure
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