On the quasi-projectivity of compactifiable strongly pseudoconvex manifolds

We construct new examples of non-Kahlerian 1-convex threefolds X with exceptional set≅P₁ (resp. ≅F₂). Also the structure of Pic(X) will be studied. On the other hand, we shall investigate the quasi-projective structure of certain Kahlerian compactifiable 1-convex manifolds; particular attention will be given to 3-fold cases through concrete examples.     

On strongly pseudoconvex manifolds with one-dimensional exceptional set

Let X be a strongly pseudoconvex n-dimensional manifold with one-dimensional connected exceptional set S. Here we show that if S is reducible, then X is embeddable into C^N ×P ^{m for some N, m and in particular X is Kählerian with a possible exception for n = 3; we analyze this exceptional case but we do not know if it may occur. The case in which S is irreducible was previously analyzed by Tan [11], who proved that X is embeddable if either n ≠ 3 or S is not isomorphic to} P ¹. In the same paper, Tan gave an example of a non-embeddable and non-Kählerian strongly pseudoconvex three-dimensional manifold withP ¹ as an exceptional set.     

Embeddability of some strongly pseudoconvex CR manifolds

We obtain an embedding theorem for compact strongly pseudoconvex CR manifolds which are boundaries of some complete Hermitian manifolds. We use this to compactify some negatively curved Kähler manifolds with compact strongly pseudoconvex boundary. An embedding theorem for Sasakian manifolds is also derived.

     

Yang-Mills connections over compact strongly pseudoconvex CR manifolds

Dedicated to Professor Noboru Tanaka in his sixtieth birthday     

On holomorphic functions of slow growth on coverings of strongly pseudoconvex manifolds

In this paper we extend some results of the paper [M. Gromov, G. Henkin, M. Shubin, Holomorphic L²-functions on coverings of pseudoconvex manifolds, Geom. Funct. Anal. 8 (1998) 552-585].     

On compactifiable strongly pseudoconvex threefolds

In contrast with the 2-dimensional case, we would like to exhibit here an example of a compactifiable strongly pseudoconvex threefold X such that a) the analytic Kodaira dimension κ(X)=3 and b) its exceptional subvariety S is projective algebraic; yet X is not quasi-projective.     

Thom-Sebastiani properties of Kohn-Rossi cohomology of compact connected strongly pseudoconvex CR manifolds

Let X_1 and X_2 be two compact connected strongly pseudoconvex embeddable Cauchy-Riemann(CR) manifolds of dimensions 2m-1 and 2n-1 in C~(m+1)and C~(n+1), respectively. We introduce the ThomSebastiani sum X = X_1 ⊕X_2which is a new compact connected strongly pseudoconvex embeddable CR manifold of dimension 2m+2n+1 in C~(m+n+2). Thus the set of all codimension 3 strongly pseudoconvex compact connected CR manifolds in Cn+1for all n 2 forms a semigroup. X is said to be an irreducible element in this semigroup if X cannot be written in the form X_1 ⊕ X_2. It is a natural question to determine when X is an irreducible CR manifold. We use Kohn-Rossi cohomology groups to give a necessary condition of the above question. Explicitly,we show that if X = X_1 ⊕ X_2, then the Kohn-Rossi cohomology of the X is the product of those Kohn-Rossi cohomology coming from X_1 and X_2 provided that X_2 admits a transversal holomorphic S~1-action.     

L 2 existence theorems for the\bar \partial _b - Neumann problem on strongly pseudoconvex CR manifoldsproblem on strongly pseudoconvex CR manifolds

LetM be the boundary of a strongly pseudoconvex domain in \(\mathbb{C}^n \) ,n≥4 and ω be an open subset inM such that ?ω is the intersection ofM with a flat hypersurface. We establish theL ² existence theorems of the \(\bar \partial _b - Neumann\) problem on ω. In particular, we prove that the \(\bar \partial _b - Laplacian\) \(\square _b = \bar \partial _b \bar \partial _b^* + \bar \partial _b^* \bar \partial _b \) equipped with a pair of natural boundary conditions, the so-called \(\bar \partial _b - Neumann\) boundary conditions, has closed range when it acts on (0,q) forms, 1≤q≤n?3. Thus there exists a bounded inverse operator for \(\square _b \) , the \(\bar \partial _b - Neumann\) operatorN _b, and we have the following Hodge decomposition theorem on ω for \(\bar \partial _b \bar \partial _b^* N_b \alpha + \bar \partial _b^* \bar \partial _b N_b \alpha \) , for any (0,q) form α withL ²(ω) coefficients. The proof depends on theL ^p regularity of the tangential Cauchy-Riemann operators \(\bar \partial _b u = \alpha \) on ω?M under the compatibility condition \(\bar \partial _b \alpha = 0\) , where α is a (p, q) form on ω, where 1≤q≤n?2. The interior regularity ofN _b follows from the fact that \(\square _b \) is subelliptic in the interior of ω. The operatorN _b induces natural questions on the regularity up to the boundary ?ω. Near the characteristic point of the boundary, certain compatibility conditions will be present. In fact, one can show thatN _b is not a compact operator onL ²(ω).     

Plurigenera of compact connected strongly pseudoconvex CR manifolds In memory of Salah Baouendi

Strongly pseudoconvex CR manifolds are boundaries of Stein varieties with isolated normal singularities.We introduce a series of new invariant plurigeneraδm,m∈Z+for a strongly pseudoconvex CR manifold.The main purpose of this paper is to present the following result:Let X1and X2be two compact strongly pseudoconvex embeddable CR manifolds of dimension 2n-1 3.If there is a non-constant CR morphism from X1to X2,thenδm(X2)δm(X1)whereδm(Xi)is the plurigeneus of Xi(see Definition 2.4).     

Explicit construction of graph invariant for strongly pseudoconvex compact 3-dimensional rational CR manifolds

Let X be a strongly pseudoconvex compact 3-dimensional CR manifolds which bounds a complex variety with isolated singularities in some C^N. The weighted dual graph of the exceptional set of the minimal good resolution of V is a CR invariant of X; in case X has a tranversal holomorphic S¹ action, we show that it is a complete topological invariant of except for two special cases. When X is a rational CR manifolds, we give explicit algebraic algorithms to compute the graph invariant in terms of the ring structure of _k=0 m^k/m^k+1, where m is the maximal ideal of each singularity. An example is computed explicitly to demonstrate how the algorithms work.     

Deformations of strongly pseudoconvex domains

We show that two smoothly bounded, strongly pseudoconvex domains which are diffeomorphic may be smoothly deformed into each other, with all intermediate domains being strongly pseudoconvex. This result relates to Lempert’s ideas about Kobayashi extremal discs, and also has intrinsic interest.     

On contact strongly pseudo-convex integrableCR manifolds

It is shown that a locally symmetric contact strongly pseudo-convex integrableCR manifold of dimension greater than 3 and other than 7 is locally isometric to a unit sphere or the Riemannian product of an (n + 1)-dimensional Euclidean space and a sphere. A conformally flat contact strongly pseudo-convex integrableCR manifold is locally isometric to a unit sphere, provided the characteristic vector field is an eigenvector of the Ricci tensor at each point.     

On normal invariants of certain manifolds

A method is presented for computing the set of homotopy classes [X, G/PL], where X is a finite CW complex satisfying certain homological conditions. The result obtained is applied to compute normal invariants of products of projective spaces.