arXiv subjects

Marc Abboud

Publications and source records attributed to Marc Abboud.

9 recordsLinked to original sources

arXiv2026

Dynamical degrees of twisted rational maps

Twisted rational maps arise naturally in relative algebraic dynamics: if a rational self-map preserves a fibration, then the induced map on the generic fiber is usually not an ordinary rational self-map over the function field, but a twisted one. This suggests that twisted rational maps form a natural framework for studying relative dynamics. In this framework we extend the theory of dynamical degrees, the numerical invariants measuring the asymptotic complexity of a dynamical system: the defining limits exist, are independent of the choice of polarization, and are birational invariants. We also identify the relative dynamical degrees of a semi-conjugacy with the dynamical degrees of the induced twisted rational map on the generic fiber, and prove the corresponding mixed degree formula. Finally, using the spectral interpretation of dynamical degrees and valuative methods at infinity, we prove an algebraicity result for the first dynamical degree of twisted endomorphisms of affine varieties.

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arXiv2026

Uniform bound on common periodic points for families of regular plane polynomial automorphisms

Given two one-dimensional families $f$ and $g$ of regular plane polynomial automorphisms parameterised by an algebraic curve $B$, all defined over some number field $K$, such that one of them is dissipative, we prove that at any parameter $b\in B(\mathbb{C})$, either $f_b$ and $g_b$ share a common iterate, or the number of their common periodic points $\mathrm{Per}(f_b) \cap \mathrm{Per}(g_b)$ is bounded by a uniform constant $D$ (independent of the parameter $b$). We thus extend a result of Mavraki and Schmidt for rational maps to our setting.

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arXiv2025

A dynamical characterisation of smooth cubic affine surfaces of Markov type

Using valuative techniques, we show that a smooth affine surface with a non-elementary automorphism group and completable by a cycle of rational curves is either the algebraic torus or a smooth cubic affine surface of Markov type. Furthermore we show that smooth cubic affine surfaces of Markov type do no admit dominant endomorphisms which are not automorphisms.

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arXiv2025

A local version of the arithmetic Hodge index theorem over quasiprojective varieties

We define a local intersection number for metrised line bundles over quasiprojective varieties with compact support and show the local arithmetic Hodge index theorem for this intersection number. As a consequence we obtain a uniqueness result for the Monge-Amp\`ere equation over quasiprojective varieties within a certain class of solutions both in the archimedean and non-archimedean setting.

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arXiv2024

Intersection of orbits of loxodromic automorphisms of affine surfaces

We show the following result: If $X_0$ is an affine surface over a field $K$ and $f, g$ are two loxodromic automorphisms with an orbit meeting infinitely many times, then $f$ and $g$ must share a common iterate. The proof uses the preliminary work of the author in [Abb23] on the dynamics of endomorphisms of affine surfaces and arguments from arithmetic dynamics. We then show a dynamical Mordell-Lang type result for surfaces in $X_0 \times X_0$.

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arXiv2024

Rigidity of periodic points for loxodromic automorphisms of affine surfaces

We show that two automorphisms of an affine surface with dynamical degree strictly larger than 1 share a Zariski dense set of periodic points if and only if they have the same periodic points. We construct canonical heights for these automorphisms and use arithmetic equidistribution for adelic line bundles over quasiprojective varieties following the work of Yuan and Zhang. When the base field is not a number field or the function field of a curve we use the theory of Moriwaki heights to prove the result.

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arXiv2024

Unlikely intersections problem for automorphisms of Markov surfaces

We study the problem of unlikely intersections for automorphisms of Markov surfaces of positive entropy. We show for certain parameters that two automorphisms with positive entropy share a Zariski dense set of periodic points if and only if they share a common iterate. Our proof uses arithmetic equidistribution for adelic line bundles over quasiprojective varieties, the theory of laminar currents and quasi-Fuchsian representation theory.

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arXiv2023

On the dynamics of endomorphisms of affine surfaces

In [FJ07], Favre and Jonsson developed tools from valuative theory to study the dynamics of a dominant endomorphism of the complex affine plane. We extend this theory to the case of any affine surface, over any field. We give a new method to construct an eigenvaluation of an endomorphism. We generalize the result of Favre and Jonsson and show that the first dynamical degree of a dominant endomorphism of a normal affine surface is an algebraic integer of degree less or equal than 2. The general method is to construct a compactification where our endomorphisms admit a fixed point at infinity where the dynamical degree can be computed by studying the local dynamics at this point. We then apply this construction to the study of the dynamics of automorphisms where we are able to say much more. In particular, we obtain a new kind of rigidity result: the set of first dynamical degrees of loxodromic automorphisms of a given affine surface must be fully contained in the set of integers or in the set of algebraic integers of degree 2.

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arXiv2022

Actions of nilpotent groups on complex algebraic varieties

We study nilpotent groups acting faithfully on complex algebraic varieties. We use a method of base change. For finite p-groups, we go from $k$, a number field, to a finite field in order to use counting lemmas. We show that a finite $p$-group of polynomial automorphisms of $k^d$ is isomorphic to a subgroup of GL$_d(k)$. For infinite groups, we go from $\mathbb{C}$ to $\mathbb{Z}_p$ and use p-adic analytic tools and the theory of p-adic Lie groups. We show that a finitely generated nilpotent group $H$ acting faithfully on a complex quasiprojective variety $X$ of dimension $d$ can be embedded into a $p$-adic Lie group acting faithfully and analytically on $\mathbb{Z}_p^d$; we deduce that $d$ is larger than the virtual derived length of $H$.

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