We classify invariant curves for birational surface maps that are expanding on cohomology. When the expansion is exponential, the arithmetic genus of an invariant curve is at most one. This implies severe constraints on both the type and number of irreducible components of the curve. In the case of an invariant curve with genus equal to one, we show that there is an associated invariant meromor...

We develop a framework to apply tropical and nonarchimedean analytic techniques to multiplication maps on linear series and study degenerations of these multiplications maps when the special fiber is not of compact type. As an application, we give a tropical criterion for a curve over a valued field to be Gieseker-Petri general.

We describe an equivalence between the notion of balanced twisted curve introduced by Abramovich and Vistoli, and a new notion of log twisted curve, which is a nodal curve equipped with some logarithmic data in the sense of Fontaine and Illusie. As applications of this equivalence, we construct a universal balanced twisted curve, prove that a balanced twisted curve over a general base scheme ad...

The modular curve X1(N) parametrizes elliptic curves with a point of order N . For N ≤ 50 we obtain plane models of X1(N) that have been optimized for fast computation, and provide explicit birational maps to transform a point on our model of X1(N) to an elliptic curve. Over a finite field, these allow us to quickly construct elliptic curves containing a point of order N , and can accelerate th...

Kodaira and Néron classified and described the geometry of the special fibers of the Néron model of an elliptic curve defined over a discrete valuation ring with a perfect residue field. Tate described an algorithm to determine the special fiber type by manipulating the Weierstrass equation. In the case of non-perfect residue fields, we discover new fiber types which are not on the Kodaira-Néro...

We show that an Anosov map has a geodesic axis on the curve graph of torus. The direct corollary our result is stable translation length always positive integer. As proof constructive, we also provide algorithm to calculate exact for any given map. application threefold: (a) determine which word realizes minimal within specific class words, (b) establish effective bound ratio lengths Teichm\"ul...

We provide a new geometric construction of pre-models (à la Ghys) for Lavaurs maps, from which we deduce that their Siegel disk is a Jordan curve running through a critical point, which was not known before. The construction turns out to work also for a class of entire maps, very specific, nonetheless including cases where no pre-models were known.

We develop a framework to apply tropical and nonarchimedean analytic methods to multiplication maps for linear series on algebraic curves, studying degenerations of these multiplications maps when the special fiber is not of compact type. As an application, we give a new proof of the GiesekerPetri Theorem, including an explicit tropical criterion for a curve over a valued field to be Gieseker-P...

Recently, a new numerical method has been proposed to compute rotation numbers of analytic circle diffeomorphisms, as well as derivatives with respect to parameters, that takes advantage of the existence of an analytic conjugation to a rigid rotation. This method can be directly applied to the study of invariant curves of planar twist maps by simply projecting the iterates of the curve onto a c...