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Marco Abate

Publications and source records attributed to Marco Abate.

34 records · Page 2Linked to original sources

Index theorems for meromorphic self-maps of the projective space

In this short note we would like to show how it is possible to use techniques introduced in the theory of local dynamics of holomorphic germs tangent to the identity to study global meromorphic self-maps of the complex projective space. In particular we shall show how a meromorphic self-map of a complex projective space induces a holomorphic foliation of the projective space in Riemann surfaces, whose singular points are exactly the fixed points and the indeterminacy points of the map; and we shall prove three index theorems, relating suitably defined local residues at the fixed and indeterminacy points with Chern classes of the projective space.

math.CV↗

Localization of Atiyah classes

We construct Atiyah classes using debar-closed forms. Under this point of view and using the Cech-Dolbeault cohomology, we provide several types of results about vanishing and localization of Atiyah classes and applications.

math.CV↗

Poincaré-Bendixson theorems for meromorphic connections and homogeneous vector fields

We first study the dynamics of the geodesic flow of a meromorphic connection on a Riemann surface, and prove a Poincaré-Bendixson theorem describing recurrence properties and $ω$-limit sets of geodesics for a meromorphic connection on $¶^1(\C)$. We then show how to associate to a homogeneous vector field $Q$ in ${\Bbb C}^n$ a rank 1 singular holomorphic foliation $\cal F$ of $¶^{n-1}(\C)$ and a (partial) meromorphic connection $\nabla^o$ along $\ca F$ so that integral curves of $Q$ are described by the geodesic flow of $\nabla^o$ along the leaves of $\ca F$, which are Riemann surfaces. The combination of these results yields powerful tools for a detailed study of the dynamics of homogeneous vector fields. For instance, in dimension two we obtain a description of recurrence properties of integral curves of $Q$, and of the behavior of the geodesic flow in a neighbourhood of a singularity, classifying the possible singularities both from a formal point of view and (for generic singularities) from a holomorphic point of view. We also get examples of unexpected new phenomena, we put in a coherent context scattered results previously known, and we obtain (as far as we know for the first time) a complete description of the dynamics in a full neighbourhood of the origin for a substantial class of 2-dimensional holomorphic maps tangent to the identity. Finally, as an example of application of our methods we study in detail the dynamics of quadratic homogeneous vector fields in $\C^2$.

math.DS↗

Carleson measures and uniformly discrete sequences in strongly pseudoconvex domains

We characterize using the Bergman kernel Carleson measures of Bergman spaces in strongly pseudoconvex bounded domains in several complex variables, generalizing to this setting theorems proved by Duren and Weir for the unit ball. We also show that uniformly discrete (with respect to the Kobayashi distance) sequences give examples of Carleson measures, and we compute the speed of escape to the boundary of uniformly discrete sequences in strongly pseudoconvex domains, generalizing results obtained in the unit ball by Jevtić, Massaneda and Thomas, by Duren and Weir, and by MacCluer.

math.CV↗

Discrete holomorphic local dynamical systems

This is a survey on local dynamics of holomorphic maps in one and several complex variables, discussing in particular normal forms and the structure of local stable sets in the non-hyperbolic case, and including several proofs and a vast bibliography. It updates and enlarge the previous survey arXiv:math/0310089v1.

math.DS↗

Isometries for the Caratheodory Metric

Under certain hypothesises, we prove that a map which is an isometry for the Caratheodory infinitesimal metric at a point is an analytic isomorphism onto its image.

math.FA↗

Embeddings of submanifolds and normal bundles

This paper is devoted to the study of the embeddings of a complex submanifold $S$ inside a larger complex manifold $M$; in particular, we are interested in comparing the embedding of $S$ in $M$ with the embedding of $S$ as the zero section in the total space of the normal bundle $N_S$ of $S$ in $M$. We explicitely describe some cohomological classes allowing to measure the difference between the two embeddings, in the spirit of the work by Grauert, Griffiths, and Camacho-Movasati-Sad; we are also able to explain the geometrical meaning of the separate vanishing of these classes. Our results holds for any codimension, but even for curves in a surface we generalize previous results due to Laufert and Camacho-Movasati-Sad.

math.CV↗

Index theorems for holomorphic maps and foliations

We describe a general construction providing index theorems localizing the Chern classes of the normal bundle of a subvariety inside a complex manifold. As particular instances of our construction we recover both Lehmann-Suwa's generalization of the classical Camacho-Sad index theorem for holomorphic foliations and our index theorem for holomorphic maps with positive dimensional fixed point set. Furthermore, we also obtain generalizations of recent index theorems of Camacho-Movasati-Sad and Camacho-Lehmann for holomorphic foliations transversal to a subvariety.

math.CV↗

Index theorems for holomorphic self-maps

Let $M$ be a complex manifold and $S\subset M$ a (possibly singular) subvariety of $M$. Let $f\colon M\to M$ be a holomorphic map such that $f$ restricted to $S$ is the identity. We show that one can associate to $f$ a holomorphic section $X_f$ of a sheaf related to the embedding of $S$ in $M$ and that such a section reads the dynamical behavior of $f$ along $S$. In particular we prove that under generic hypotheses the canonical section $X_f$ induces a holomorphic action in the sense of Bott on the normal bundle of (the regular part of) $S$ in $M$ and this allows to obtain for holomorphic self-maps with non- isolated fixed points index theorems similar to Camacho-Sad, Baum-Bott and variation index theorems for holomorphic foliations. Finally we apply our index theorems to obtain information about topology and dynamics of holomorphic self-maps of surfaces with a compact curve of fixed points.

math.DS↗

Formal normal forms for holomorphic maps tangent to the identity

We describe a procedure for constructing formal normal forms of holomorphic maps with a hypersurface of fixed points, and we apply it to obtain a complete list of formal normal forms for 2-dimensional holomorphic maps tangential to a curve of fixed points.

math.DS↗

Ritt's theorem and the Heins map in hyperbolic complex manifolds

Let X be a Kobayashi hyperbolic complex manifold, and assume that X does not contain compact complex submanifolds of positive dimension (e.g., X Stein). We shall prove the following generalization of Ritt's theorem: every holomorphic self-map f of X such that f(X) is relatively compact in X has a unique fixed point p(f) in X, which is attracting. Furthermore, we shall prove that p(f) depends holomorphically on f in a suitable sense, generalizing results by Heins, Joseph-Kwack and the second author.

math.CV↗

Discrete local holomorphic dynamics

This is a survey on the local structure about a fixed point of discrete finite-dimensional holomorphic dynamical systems, discussing in particular the existence of local topological conjugacies to normal forms, and the structure of local stable sets in the non-hyperbolic case. The author hopes to keep the survey up to date, and thus it would be grateful to anybody pointing out missing (or mistaken) results and references, and/or suggesting topics to be included or expanded in it.

math.DS↗

Diagonalization of non-diagonalizable discrete holomorphic dynamical systems

We describe a canonical procedure for associating to any (germ of) holomorphic self-map f of C^n fixing the origin such that df_O is invertible and non-diagonalizable an n-dimensional complex manifold M, a holomorphic map p from M to C^n, a point e in M and a (germ of) holomorphic self-map F of M so that: p restricted to the complement of p^{-1}(O) is a biholomorphism between this complement and C^n minus the origin; p semiconjugates f and F; and e is a fixed point of F such that dF_e is diagonalizable. Furthermore, we use this construction to describe the local dynamics of such an f nearby the origin when the only eigenvalue of df_O is 1.

math.CV↗

The Julia-Wolff-Caratheodory theorem in polydisks

The classical Julia-Wolff-Caratheodory theorem gives a condition ensuring the existence of the non-tangential limit of both a bounded holomorphic function and its derivative at a given boundary point of the unit disk in the complex plane. This theorem has been generalized by Rudin to holomorphic maps between unit balls in C^n, and by the author to holomorphic maps between strongly (pseudo)convex domains. Here we describe Julia-Wolff-Caratheodory theorems for holomorphic maps defined in a polydisk and with image either in the unit disk, or in another polydisk, or in a strongly convex domain. One of main tool for the proof is a general version of Lindelof's principle valid for not necessarily bounded holomorphic functions.

math.CV↗

Complex Finsler metrics

In this paper we describe an approach to complex Finsler metrics suitable to deal with global questions, and stressing the similarities between hermitian and complex Finsler metrics. Let $F$ be a smooth complex Finsler metric on a complex manifold $M$, and assume that the indicatrices of $F$ are strongly pseudoconvex -- we shall say that $F$ itself is strongly pseudoconvex. The vertical bundle $\cal V$ is the kernel of the differential of the canonical projection of the holomorphic tangent bundle of $M$. Using $F$, it is possible to endow $\cal V$ with a hermitian metric; let $D$ be the Chern connection associated to this metric. It turns out that there is a canonical way to build starting from $D$ a horizontal bundle $\cal H$, as well as a bundle isomorphism $Θ\colon{\cal V}\to\cal H$. Using $Θ$ we may transfer both the metric and the connection on $\cal H$; furthermore, there is a canonical isometric embedding $χ$ of the holomorphic tangent bundle of $M$ into $\cal H$. Our idea is that the Finsler geometry of $M$ can be studied applying standard hermitian techniques to $\cal H$ using $χ$ to transfer back and forth problems and solutions. To support this claim, in this paper we discuss Bianchi identities, Kähler conditions, the first and second variation formulas, geodesics and holomorphic curvature. Furthermore, we provide a sound geometric interpretation to our previous work on the existence of complex geodesic curves. Finally, we prove that in complex Kähler Finsler manifolds with constant nonpositive holomorphic curvature (and satisfying an additional symmetry property on the curvature) the complex geodesic curves define a nice fibration of the manifold, completely analogous to the one described by Lempert in strongly convex domains.

math.CV↗

Holomorphic curvature of Finsler metrics and complex geodesics

In his famous 1981 paper, Lempert proved that given a point in a strongly convex domain the complex geodesics (i.e., the extremal disks) for the Kobayashi metric passing through that point provide a very useful fibration of the domain. In this paper we address the question whether, given a smooth complex Finsler metric on a complex manifold, it is possible to give purely differential geometric properties of the metric ensuring the existence of such a fibration in complex geodesics of the manifold. We first discuss at some length the notion of holomorphic sectional curvature for a complex Finsler metric; then, using the differential equation of complex geodesics we obtained in a previous paper, we show that for every pair (point, tangent vector) there is a (only a segment if the metric is not complete) complex geodesic passing through the point tangent to the given vector iff the Finsler metric is Kähler, has constant holomorphic sectional curvature -4 and satisfies a simmetry condition on the curvature tensor. Finally, we show that a complex Finsler metric of constant holomorphic sectional curvature -4 satisfying the given simmetry condition on the curvature is necessarily the Kobayashi metric.

math.CV↗