arXiv subjects

Alejo García-Sassi

Publications and source records attributed to Alejo García-Sassi.

3 recordsLinked to original sources

arXiv2026

Fully chaotic conservative models for some torus homeomorphisms

We study homotopic-to-the-identity torus homeomorphisms, whose rotation set has nonempty interior. We prove that any such map is monotonically semiconjugate to a homeomorphism that preserves the Lebesgue measure, and that has the same rotation set. Furthermore, the dynamics of the quotient map has several interesting chaotic traits: for instance, it is topologically mixing, has a dense set of periodic points and is continuum-wise expansive. In particular, this shows that a convex compact set of $\mathbb{R}^2$ with nonempty interior is the rotation set of the lift of a homeomorphism of $\mathbb{T}^2$ if and only if it is the rotation set of the lift of a conservative homeomorphism.

math.DS↗

arXiv2024

Geodesic tracking and the shape of ergodic rotation sets

We prove a structure theorem for ergodic homological rotation sets of homeomorphisms isotopic to the identity on a closed orientable hyperbolic surface: this set is made of a finite number of pieces that are either one-dimensional or almost convex. The latter ones give birth to horseshoes; in the case of a zero-entropy homeomorphism we show that there exists a geodesic lamination containing the directions in which generic orbits with respect to ergodic invariant probabilities turn around the surface under iterations of the homeomorphism. The proof is based on the idea of $\textit{geodesic tracking}$ of orbits that are typical for some invariant measure by geodesics on the surface, that allows to get links between the dynamics of such points and the one of the geodesic flow on some invariant subset of the unit tangent bundle of the surface.

math.DS↗

arXiv2019

Fixed points for branched covering maps of the plane

A well-known result from Brouwer states that any orientation preserving homeomorphism of the plane with no fixed points has an empty non-wandering set. In particular, an invariant compact set implies the existence of a fixed point. In this paper we give sufficient conditions for degree 2 branched covering maps of the plane to have a fixed point, namely: A totally invariant compact subset such that it does not separate the critical point from its image An invariant compact subset with a connected neighbourhood $U$, such that $\mathrm{Fill}(U \cup f(U))$ does not contain the critical point nor its image. An invariant continuum such that the critical point and its image belong to the same connected component of its complement.

math.DS↗