CR foliations,the strip-problem and Globevnik–Stout conjecture

We characterize CR functions on planar domains and real hypersurfaces in ${\mathbb{C}}^2$ in terms of analytic extendibility into attached analytic discs. It is done by studying propagation, from the boundary into interior, of degeneracy of CR foliations of solid torus-like manifolds. In particular, we answer, for smooth functions, two open questions mentioned in the title: about characterization of analytic functions in the complex plane and about characterization of boundary values of holomorphic functions in bounded domains in ${\mathbb{C}}^n$. To cite this article: M. Agranovsky, C. R. Acad. Sci. Paris, Ser. I 343 (2006).     

On Analytic Interpolation Manifolds in Boundaries of Weakly Pseudoconvex Domains

Let Ω be a bounded, weakly pseudoconvex domain in C ⁿ , n ≤ 2, with real-analytic boundary. A real-analytic submanifold M ? ?Ω is called an analytic interpolation manifold if every real-analytic function on M extends to a function belonging to (Ω¯). We provide sufficient conditions for M to be an analytic interpolation manifold. We give examples showing that neither of these conditions can be relaxed, as well as examples of analytic interpolation manifolds lying entirely within the set of weakly pseudoconvex points of ?Ω.     

Compactness of Hankel operators and analytic discs in the boundary of pseudoconvex domains

Using several complex variables techniques, we investigate the interplay between the geometry of the boundary and compactness of Hankel operators. Let β be a function smooth up to the boundary on a smooth bounded pseudoconvex domain Ω⊂Cn. We show that, if Ω is convex or the Levi form of the boundary of Ω is of rank at least n−2, then compactness of the Hankel operator Hβ implies that β is holomorphic “along” analytic discs in the boundary. Furthermore, when Ω is convex in C² we show that the condition on β is necessary and sufficient for compactness of Hβ.     

A theorem in complex symplectic geometry

We prove that two simple, closed, real-analytic curves in C²ⁿ that are polynomially convex are equivalent under the group of symplectic holomorphic automorphisms of C²ⁿ if and only if the two curves have the same action integral. Every two simple real-analytic arcs in C²ⁿ are so equivalent.     

Testing holomorphy on curves

For a domain D ? ? ⁿ we construct a continuous foliation of D into one-real-dimensional curves such that any function f ∈ C ¹(D) which can be extended holomorphically into some neighborhood of each curve in the foliation will be holomorphic on D.     

Finite jet determination of CR mappings

We prove the following finite jet determination result for CR mappings: Given a smooth generic submanifold M⊂CN, N?2, that is essentially finite and of finite type at each of its points, for every point p∈M there exists an integer ?p, depending upper-semicontinuously on p, such that for every smooth generic submanifold M^′⊂CN of the same dimension as M, if are two germs of smooth finite CR mappings with the same ?p jet at p, then necessarily for all positive integers k. In the hypersurface case, this result provides several new unique jet determination properties for holomorphic mappings at the boundary in the real-analytic case; in particular, it provides the finite jet determination of arbitrary real-analytic CR mappings between real-analytic hypersurfaces in CN of D'Angelo finite type. It also yields a new boundary version of H. Cartan's uniqueness theorem: if Ω,Ω^′⊂CN are two bounded domains with smooth real-analytic boundary, then there exists an integer k, depending only on the boundary ∂Ω, such that if are two proper holomorphic mappings extending smoothly up to ∂Ω near some point p∈∂Ω and agreeing up to order k at p, then necessarily H₁=H₂.     

Branching laws for discrete Wallach points

We consider the (projective) representations of the group of holomorphic automorphisms of a symmetric tube domain V⊕iΩ that are obtained by analytic continuation of the holomorphic discrete series. For a representation corresponding to a discrete point in the Wallach set, we find the decomposition under restriction to the identity component of GL(Ω). Using Riesz distributions, an explicit intertwining operator is constructed as an analytic continuation of an integral operator. The density of the Plancherel measure involves quotients of Γ-functions and the c-function for a symmetric cone of smaller rank.     

Analytic sets extending the graphs of holomorphic mappings

Let D, D′ ⊂ ℂⁿ be bounded domains with smooth real analytic boundaries and ƒ: D → D′ be a proper holomorphic map. Our main result implies that if the graph of ƒ extends as an analytic set to a neighborhood of a poìnt (a, a′) ∈ ∂D × 3D′ with a′ ∈ cl_ƒ(a), then ƒ extends holomorphically to a neighborhood of a.     

On the unique continuation problem for CR mappings into nonminimal hypersurfaces

We prove the following results on the unique continuation problem for CR mappings between real smooth hypersurfaces in ? ⁿ . If the CR mappingH extends holomorphically to one side of the source manifoldM near the pointp ₀ εM, the target manifoldM′ contains a holomorphic hypersurface σ′ throughp′₀ =H(p ₀ (i.e.,M′ is nonminimal atp′ ₀), andH(M) ? Σ′ (forcingM to be nonminimal atp ₀), then the transversal component ofH is not flat atp ₀. Furthermore, we show that the assumption thatH extends holomorphically to one side ofM cannot be removed in general. Indeed, we give an example of a smooth CR mappingH, withM, M′ ? ?², real analytic and of infinite type atp ₀ andp′₀ respectively (without being Levi flat), such thatH(M) ? Σ′ but the transversal component ofH is flat atp ₀ (in particular,H is not real analytic!). However, we show that ifM andM′ are assumed to be real analytic, and if the sourceM is “sufficiently far from being Levi flat” in a certain sense (so as to exclude the above mentioned counterexample) then the assumption thatH extends holomorphically to one side ofM can be dropped. Also, in the general case, we prove that the rate of vanishing of the transversal component cannot be too rapid (unlessH(M) ? Σ′), and we relate the possible rate of vanishing to the order of vanishing of the Levi form on a certain holomorphic submanifold ofM.     

Defect and evaluations

Let S be a generic submanifold of C ^N of real codimension m. In this paper we continue the study, carried over by various authors, of the set of analytic discs attached to S. Moreover, we look at the subspaces of C ^N obtained by evaluating at given points, holomorphic maps which are infinitesimal deformations of analytic discs attached to S.     

One Boundary Version of Morera's Theorem

Let D be a bounded domain in C ⁿ (n>1) with a connected smooth boundary D and let f be a continuous function on D. We consider conditions (generalizing those of the Hartogs–Bochner theorem) for holomorphic extendability of f to D. As a corollary we derive some boundary analog of Morera's theorem claiming that if the integrals of f vanish over the intersection of the boundary of the domain with complex curves in some class then f extends holomorphically to the domain.     

On a boundary analog of the Forelli theorem

A boundary analog of the Forelli theorem for real-analytic functions is established, i.e., it is demonstrated that each real-analytic function f defined on the boundary of a bounded strictly convex domain D in the multidimensional complex space with the one-dimensional holomorphic extension property along families of complex lines passing through a boundary point and intersecting D admits a holomorphic extension to D as a function of many complex variables.     

Extremal discs and holomorphic extension from convex hypersurfaces

Let D be a convex domain with smooth boundary in complex space and let f be a continuous function on the boundary of D. Suppose that f holomorphically extends to the extremal discs tangent to a convex subdomain of D. We prove that f holomorphically extends to D. The result partially answers a conjecture by Globevnik and Stout of 1991.     

Extending Solutions of Holomorphic Partial Differential Equations Across Real Hypersurfaces

The main result in this paper, Theorem 1.2, generalizes a theoremof Zerner [26] concerning sufficient conditions for the holomorphiccontinuability of a solution of a linear holomorphic partialdifferential equation across a point of a hypersurface, on oneside of which it is holomorphic. The point of the new theoremis, roughly speaking, that it applies also to regular solutionsof partial differential equations whose coefficients may havecertain kinds of singularities. This enables us to deduce somenew results (see 2) on elliptic partial differential equationsin R²:Theorem 2.1 extends a result of Vekua on the size of thedomain of holomorphy of solutions to elliptic equations, inthe case where singularities are permitted in the coefficients;Theorem 2.2 is of an apparently novel type, showing (roughly)that under certain conditions the solution to Cauchy's problemis real-analytic in a domain whose size depends only on theprincipal part of the operator, which is assumed to be the Laplacian,and the Cauchy data on the real axis. (Results of this kindare very delicate, as we shall illustrate in 4 with a simplecounterexample.) Theorem 2.2 is new and non-trivial even forequations with analytic coefficients, in which case though,Theorem 1.2 is not needed for the proof.     

An algebraic characterization of holomorphic nondegeneracy for real algebraic hypersurfaces and its application to CR mappings

We give a new algebraic characterization of holomorphic nondegeneracy for embedded real algebraic hypersurfaces in , . We then use this criterion to prove the following result about real analyticity of smooth CR mappings: any smooth CR mapping H between a real analytic hypersurface and a rigid polynomial holomorphically nondegenerate hypersurface is real analytic, provided the map H is not totally degenerate in the sense of Baouendi and Rothschild. Received September 19, 1997     

Analyticity on families of circles

It is known that iff is a continuous function on the complex plane which extends holomorphically from each circle surrounding the origin, thef is not necessarily holomorphic. In the paper we prove that if, in addition,f extends holomorphically from each circle belonging to an open family of circles which do not surround the origin, thef is holomorphic.     

Composition operators induced by smooth self-maps of the real or complex unit balls

In this paper, we study the composition operator CΦ with a smooth but not necessarily holomorphic symbol Φ. A necessary and sufficient condition on Φ for CΦ to be bounded on holomorphic (respectively harmonic) weighted Bergman spaces of the unit ball in Cn (respectively Rn) is given. The condition is a real version of Wogen's condition for the holomorphic spaces, and a non-vanishing boundary Jacobian condition for the harmonic spaces. We also show certain jump phenomena on the weights for the target spaces for both the holomorphic and harmonic spaces.     

Similarity classification of holomorphic curves

Let H be a complex separable Hilbert space. For Ω an open connected subset of C, we shall say that a map is a holomorphic curve, if there exist n holomorphic H-valued functions γ₁,γ₂,…,γn on Ω such that f(λ)=?{γ₁(λ),…,γn(λ)}, ∀λ∈Ω, where Gr(n,H) denotes the Grassmann manifold, the set of all n-dimensional subspaces of H.In the paper, we give a similarity classification of some holomorphic curves by using the K-group of its commutant algebra as an invariant.     

Parametric H-principle for holomorphic immersions with approximation

We prove the parametric homotopy principle for holomorphic immersions of Stein manifolds into Euclidean space and the homotopy principle with approximation on holomorphically convex sets. We write an integration by parts like formula for the solution f to the problem LfΣ_|=g, where L is a holomorphic vector field, semi-transversal to analytic variety Σ.     

Two modularity lifting conjectures for families of Siegel modular forms

For a prime p and a positive integer n, using certain lifting procedures, we study some constructions of p-adic families of Siegel modular forms of genus n. Describing L-functions attached to Siegel modular forms and their analytic properties, we formulate two conjectures on the existence of the modularity liftings from GSp _r × GSp_2m to GSp _r+2m for some positive integers r and m.