Viser treff 1-10 av 31
Dynamics and entropy in the Zhang model of Self-Organized Criticality
(Working paper; Arbeidsnotat, 2005-09-12)
We give a detailed study of dynamical properties of the Zhang model, including evaluation of topological entropy and estimates for the Lyapunov exponents and the dimension of the attractor. In the thermodynamic limit the entropy goes to zero and the Lyapunov spectrum collapses.1
Entropy via multiplicity
(Working paper; Arbeidsnotat, 2005-09-30)
The topological entropy of piecewise affine maps is studied. It is shown that singularities may contribute to the entropy only if there is angular expansion and we bound the entropy via the expansion rates of the map. As a corollary we deduce that non-expanding conformal piecewise affine maps have zero topological entropy. We estimate the entropy of piecewise affine skew-products. Examples of ...
A piece-wise affine contracting map with positive entropy
(Working paper; Arbeidsnotat, 2005-04-10)
We construct the simplest chaotic system with a two-point attractor.
Examples of integrable sub-Riemannian geodesic flows
(Journal article; Tidsskriftartikkel; Peer reviewed, 2001-10-22)
We exhibit examples of sub-Riemannian metrics with integrable geodesic flows and positive topological entropy.
Existence of close pseudoholomorphic disks for almost complex manifolds and an applications to Kobayashi-Royden pseudonorm
(Journal article; Tidsskriftartikkel; Peer reviewed, 2000-02-23)
It is proved in the paper that near every pseudoholomorphic disk on an almost complex manifold a disk of almost the same size in any close direction passes. As an application the Kobayashi-Royden pseudonorm for almost complex manifolds is defined and studied.
Invariants and submanifolds in almost complex geometry
(Chapter; Bokkapittel, 2007-12-20)
In this paper we describe the algebra of differential invariants for GL(n,C)-structures. This leads to classification of almost complex structures of general positions. The invariants are applied to the existence problem of higher-dimensional pseudoholomorphic submanifolds.
Deformation of big pseudoholomorphic disks and application to the Hanh pseudonorm
(Journal article; Tidsskriftartikkel; Peer reviewed, 2003-04-14)
We simplify proof of the theorem that close to any pseudoholomorphic disk there passes a pseudoholomorphic disk of arbitrary close size with any pre-described sufficiently close direction. We apply these results to the Kobayashi and Hanh pseudodistances. It is shown they coincide in dimensions higher than four. The result is new even in the complex case.
Invariant characterization of Liouville metrics and polynomial integrals
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007-09-04)
A criterion in terms of differential invariants for a metric on a surface to be Liouville is established. Moreover, in this paper we completely solve in invariant terms the local mobility problem of a 2D metric, considered by Darboux: How many quadratic in momenta integrals does the geodesic flow of a given metric possess? The method is also applied to recognition of other polynomial integrals ...
Nijenhuis tensors in pseudoholomorphic curves neighborhoods
(Working paper; Arbeidsnotat, 2000)
In this paper we consider the normal forms of almost complex structures in a neighborhood of pseudoholomorphic curve. We define normal bundles of such curves and study the properties of linear bundle almost complex structures. We describe 1-jet of the almost complex structure along a curve in terms of its Nijenhuis tensor. For pseudoholomorphic tori we investigate the problem of pseudoholomorphic ...
Strictly non-proportional geodesically equivalent metrics have htop(g) = 0
(Journal article; Tidsskriftartikkel; Peer reviewed, 2004-10-24)
If a closed manifold M possesses two Riemannian metrics which have the same unparameterized geodesics and are not strictly proportional at each point, then the topological entropy of both geodesic flows is zero. This is the main result of the paper and it has many dynamical and topological corollaries. In particular, such a manifoldM should be finitely covered by the product of a rationally ...