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Francine Meylan

Publications and source records attributed to Francine Meylan.

At least 19 recordsLinked to original sources
arXiv2025

New examples of CR submanifolds for the $2$-jet determination problem

This paper addresses two questions related to mapping problems. In the first part of the paper, we discuss some recent results regarding the $2$-jet determination for biholomorphisms between smooth (weakly) pseudoconvex hypersurfaces; in light of those, we formulate a general problem and illustrate it with examples. In the second part of the paper, we provide a new example of a real submanifold of codimension $7$ in $\mathbb{C}^{10}$ that is not strictly pseudoconvex and for which its germs of CR automorphisms are determined by their $2$-jets at a given point.

math.CV↗
arXiv2025

Classification of polynomial models without 2-jet determination in $\mathbb{C}^3$

An intriguing phenomenon regarding Levi-degenerate hypersurfaces is the existence of nontrivial infinitesimal symmetries with vanishing 2-jets at a point. In this work we consider polynomial models of Levi-degenerate real hypersurfaces in $\mathbb{C}^3$ of finite Catlin multitype. Exploiting the structure of the corresponding Lie algebra, we characterize completely models without 2-jet determination, including an explicit description of their symmetry algebras.

math.CV↗
arXiv2023

Characterization of real-analytic infinitesimal CR automorphisms for a class of hypersurfaces in $\Bbb C^4.$

In this paper, motivated by the work of Kim and Kolar for the case of pseudoconvex models which are sums of squares of polynomials, we study the Lie algebra of real-analytic infinitesimal $CR$ automorphisms of a model hypersurface $M_0$ given by \begin{equation} M_0= \{(z,w) \in \mathbb C^{3} \times \mathbb C \ | \ \Im w= P\bar Q + Q\bar P + R\bar R \}, \end{equation} where $P,$ $Q$ and $R$ are homogeneous polynomials. In particular, we classify $M_0$ with respect to the description of its nilpotent rotations when $P,$ $Q$ and $R$ are monomials. We also give an example of a model $M_0$ for which the real dimension of its generalized (exotic) rotations is $3.$

math.CV↗
arXiv2022

Chern-Moser operators and weighted jet determination problems in higher codimension

Counterexamples to the 2-jet determination Chern-Moser Theorem in codimension d>2 have recently been constructed. We extend the Chern-Moser approach for hypersurfaces to real submanifolds of higher codimension in complex space to derive results on jet determination for their automorphism group. Using these techniques, we show that the 2-jet determination Chern-Moser Theorem holds in codimension 2.

math.CV↗
arXiv2021

The 1-jet determination of stationary discs attached to generic CR submanifolds

The existence of a nondefective stationary disc attached to a nondegenerate model quadric in C^N is a necessary condition to ensure the unique 1-jet determination of the lifts of a key family of stationary discs. In this paper, we give an elementary proof of the equivalence when the model quadric is strongly pseudoconvex, recovering a result of Tumanov. Our proof is based on the explicit expression of stationary discs, and opens up a conjecture for the unique 1-jet determination to hold when the model is not necessarily strongly pseudoconvex.

math.CV↗
arXiv2021

Explicit construction of stationary discs and its consequences for nondegenerate quadrics

We give an explicit construction of a key family of stationary discs attached to a nondegenerate model quadric in $\mathbb{C}^N$ and derive a necessary condition for which (each lift) of those stationary discs is uniquely determined by its $1$-jet at a given point via a local diffeomorphism. This unique $1$-jet determination is a crucial step to deduce $2$-jet determination for CR automorphisms of generic real submanifolds in $\mathbb{C}^N$.

math.CV↗
arXiv2020

Construction of counterexamples to the $2-$jet determination Chern-Moser Theorem in higher codimension

We first construct a counterexample of a generic quadratic submanifold of codimension $5$ in $\Bbb C^9$ which admits a real analytic infinitesimal CR automorphism with homogeneous polynomial coefficients of degree $4.$ This example also resolves a question in the Tanaka prolongation theory that was open for more than 50 years. Then we give sufficient conditions to generate more counterexamples to the $2-$jet determination Chern-Moser Theorem in higher codimension. In particular, we construct examples of generic quadratic submanifolds with jet determination of arbitrarily high order.

math.CV↗
arXiv2020

Nonlinearizable CR automorphisms for polynomial models in $\mathbb C^N$

We classify polynomial models for real hypersurfaces in $\mathbb C^N$, which admit nonlinearizable infinitesimal CR automorphisms. As a consequence, this provides an optimal 1-jet determination result in the general case. Further we prove that such automorphisms arise from one common source, by pulling back via a holomorphic mapping a suitable symmetry of a hyperquadric in some complex space.

math.CV↗
arXiv2017

Nonlinear CR automorphisms of Levi degenerate hypersurfaces and a new gap phenomenon

We give a complete classification of polynomial models for smooth real hypersurfaces of finite Catlin multitype in $\mathbb C^3$, which admit nonlinear infinitesimal CR automorphisms. As a consequence, we obtain a sharp 1-jet determination result for any smooth hypersurface with such model. The results also prove a conjecture of the first author about the origin of such nonlinear automorphisms (AIM list of problems, 2010). As another consequence, we describe all possible dimensions of the Lie algebra of infinitesimal CR automorphisms, which leads to a new "secondary" gap phenomenon.

math.CV↗
arXiv2015

Higher order symmetries of real hypersurfaces in $\Bbb C^3.$

We study nonlinear automorphisms of Levi degenerate hypersurfaces of finite multitype. By recent results of Kolar, Meylan and Zaitsev, the Lie algebra of infinitesimal CR automorphisms may contain a graded component consisting of nonlinear vector fields of arbitrarily high degree, which has no analog in the classical Levi nondegenerate case, or in the case of finite type hypersurfaces in $\mathbb C^2$. We analyze this phenomenon for hypersurfaces of finite Catlin multitype in complex dimension three. The results provide a complete classification of such manifolds. As a consequence, we show on which hypersurfaces 2-jets are not sufficient to determine an automorphism. The results also confirm a conjecture about the origin of nonlinear automorphisms of Levi degenerate hypersurfaces, formulated by the first author (AIM 2010).

math.CV↗