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Dmitri Zaitsev

Publications and source records attributed to Dmitri Zaitsev.

At least 37 records · Page 2Linked to original sources
arXiv2014

Rigidity of proper holomorphic maps between bounded symmetric domains

Our first main result gives assumptions guaranteeing that proper holomorphic maps between Cartan type I bounded symmetric domains have simple block matrix shape, answering positively a question of Mok. The proof is based on the second main result establishing similar phenomenon for local CR maps between arbitrary boundary components of two bounded symmetric domains of the above type. Since boundary components other than Shilov boundaries are Levi-degenerate, our analysis is based on their $2$-nondegeneracy combining Levi forms with higher order tensors.

math.CV↗
arXiv2013

Rigidity of CR maps between Shilov boundaries of bounded symmetric domains

Our goal is to establish what seems to be the first rigidity result for CR embeddings between Shilov boundaries of bounded symmetric domains of higher rank. The result states that any such CR embedding is the standard linear embedding up to CR automorphisms. Our basic assumption extends precisely the well-known optimal bound for the rank one case. There are no other restrictions on the ranks, in particular, the difficult case when the target rank is larger than the source rank is also allowed.

math.CV↗
arXiv2013

Factoring Formal Maps into Reversible or Involutive Factors

An element $g$ of a group is called reversible if it is conjugate in the group to its inverse. An element is an involution if it is equal to its inverse. This paper is about factoring elements as products of reversibles in the group $\mathfrak{G}_n$ of formal maps of $(\mathbb{C}^n,0)$, i.e. formally-invertible $n$-tuples of formal power series in $n$ variables, with complex coefficients. The case $n=1$ was already understood. Each product $F$ of reversibles has linear part $L(F)$ of determinant $\pm1$. The main results are that for $n\ge2$ each map $F$ with det$(L(F))=\pm1$ is the product of $2+3c$ reversibles, and may also be factored as the product of $9+6c$ involutions, where $c$ is the smallest integer $\ge \log_2n$.

math.GR↗
arXiv2013

Non-embeddable Real Algebraic Hypersurfaces

We study various classes of real hypersurfaces that are not embeddable into more special hypersurfaces in higher dimension, such as spheres, real algebraic compact strongly pseudoconvex hypersurfaces or compact pseudoconvex hypersurfaces of finite type. We conclude by stating some open problems.

math.CV↗
arXiv2012

Dynamics of multi-resonant biholomorphisms

The goal of this paper is to study the dynamics of holomorphic diffeomorphisms in C^n such that the resonances among the first 1<= r<= n eigenvalues of the differential are generated over N by a finite number of Q-linearly independent multi-indices (and more resonances are allowed for other eigenvalues). We give sharp conditions for the existence of basins of attraction where a Fatou coordinate can be defined. Furthermore, we obtain a generalization of the Leau-Fatou flower theorem, providing a complete description of the dynamics in a full neighborhood of the origin for 1-resonant parabolically attracting holomorphic germs in Poincare'-Dulac normal form.

math.CV↗
arXiv2011

Dynamics of one-resonant biholomorphisms

Our first main result is a construction of a simple formal normal form for holomorphic diffeomorphisms in C^n whose differentials have one-dimensional family of resonances in the first m eigenvalues, m <= n (but more resonances are allowed for other eigenvalues). Next, we provide invariants and give conditions for the existence of basins of attraction. Finally, we give applications and examples demonstrating the sharpness of our conditions.

math.CV↗
arXiv2009

Formal and finite order equivalences

We show that two families of germs of real-analytic subsets in $C^{n}$ are formally equivalent if and only if they are equivalent of any finite order. We further apply the same technique to obtain analogous statements for equivalences of real-analytic self-maps and vector fields under conjugations. On the other hand, we provide an example of two sets of germs of smooth curves that are equivalent of any finite order but not formally equivalent.

math.CV↗
arXiv2009

Boundary problem for Levi flat graphs

In an earlier paper the authors provided general conditions on a real codimension 2 submanifold $S\subset C^{n}$, $n\ge 3$, such that there exists a possibly singular Levi-flat hypersurface $M$ bounded by $S$. In this paper we consider the case when $S$ is a graph of a smooth function over the boundary of a bounded strongly convex domain $Ω\subset C^{n-1}\times R$ and show that in this case $M$ is necessarily a graph of a smooth function over $Ω$. In particular, $M$ is non-singular.

math.CV↗
arXiv2009

On Levi-flat hypersurfaces with prescribed boundary

We address the problem of existence and uniqueness of a Levi-flat hypersurface $M$ in $C^n$ with prescribed compact boundary $S$ for $n\ge3$. The situation for $n\ge3$ differs sharply from the well studied case $n=2$. We first establish necessary conditions on $S$ at both complex and CR points, needed for the existence of $M$. All CR points have to be nonminimal and all complex points have to be "flat". Then, adding a positivity condition at complex points, which is similar to the ellipticity for $n=2$ and excluding the possibility of $S$ to contain complex $(n-2)$-dimensional submanifolds, we obtain a solution $M$ to the above problem as a projection of a possibly singular Levi-flat hypersurface in $R\times C^n$. It turns out that $S$ has to be a topological sphere with two complex points and with compact CR orbits, also topological spheres, serving as boundaries of the (possibly singular) complex leaves of $M$. There are no more global assumptions on $S$ like being contained in the boundary of a strongly pseudoconvex domain, as it was in case $n=2$. Furthermore, we show in our situation that any other Levi-flat hypersurface with boundary $S$ must coincide with the constructed solution.

math.CV↗
arXiv2009

New normal forms for Levi-nondegenerate hypersurfaces

In this paper we construct a large class of new normal forms for Levi-nondegenerate real hypersurfaces in complex spaces. We adopt a general approach illustrating why these normal forms are natural and which role is played by the celebrated Chern-Moser normal form. The latter appears in our class as the one with the "maximum normalization" in the lowest degree. However, there are other natural normal forms, even with normalization conditions for the terms of the same degree. Some of these forms do not involve the cube of the trace operator and, in that sense, are simplier than the one by Chern-Moser. We have attempted to give a complete and self-contained exposition (including proofs of well-known results about trace decompositions) that should be accessible to graduate students.

math.CV↗
arXiv2007

Obstructions to embeddability into hyperquadrics and explicit examples

We give series of explicit examples of Levi-nondegenerate real-analytic hypersurfaces in complex spaces that are not transversally holomorphically embeddable into hyperquadrics of any dimension. For this, we construct invariants attached to a given hypersurface that serve as obstructions to embeddability. We further study the embeddability problem for real-analytic submanifolds of higher codimension and answer a question by Forstnerič.

math.CV↗
arXiv2006

Lie group structures on automorphism groups of real-analytic CR manifolds

Given any real-analytic CR manifold M, we provide general conditions on M guaranteeing that the group of all its global real-analytic CR automorphisms is a Lie group (in an appropriate topology). Our conditions are in particular satisfied when M is an arbitrary compact real-analytic hypersurface embedded in some Stein manifold.

math.CV↗
arXiv2006

On different notions of homogeneity for CR-manifolds

We show that various notions of local homogeneity for CR-manifolds are equivalent. In particular, if germs at any two points of a CR-manifold are CR-equivalent, there exists a transitive local Lie group action by CR-automorphisms near every point.

math.CV↗
arXiv2006

Boundary jets of holomorphic maps between strongly pseudoconvex domains

We study jets of germs of holomorphic maps between two strongly pseudoconvex domains under the condition that the image of one domain is contained into the other and a given boundary point is (non-tangentially) mapped to a given boundary point. We completely characterize the (non-tangential) 1-jets. Moreover we give algebraic inequalities (in terms of Chern-Moser normal forms up to a certain low order) for the admissible germs with a given 1-jet. Also, we prove a rigidity result which says that there exists a germ tangent to the Identity (in some local charts) if and only if the two domains are tangent up to weighted order five.

math.CV↗
arXiv2004

On local CR-transformations of Levi-degenerate group orbits in compact Hermitian symmetric spaces

Let $S$ be a real-analytic hypersurface in $C^n$ or, more generally, a CR-submanifold in a complex manifold $Z$ of arbitrary CR-codimension. This paper addresses the question, when a local biholomorphic map between open sets in $Z$ sending an open piece of $S$ into $S$ extends to a global biholomorphic self-map of $Z$ preserving $S$. We give answers for a large class of Levi-degenerate group orbits in compact Hermitian symmetric spaces.

math.CV↗
arXiv2002

Rigidity of CR-immersions into spheres

We consider local CR-immersions of a strictly pseudoconvex real hypersurface $M\subset\bC^{n+1}$, near a point $p\in M$, into the unit sphere $\mathbb S\subset\bC^{n+d+1}$ with $d>0$. Our main result is that if there is such an immersion $f\colon (M,p)\to \mathbb S$ and $d < n/2$, then $f$ is {\em rigid} in the sense that any other immersion of $(M,p)$ into $\mathbb S$ is of the form $ϕ\circ f$, where $ϕ$ is a biholomorphic automorphism of the unit ball $\mathbb B\subset\bC^{n+d+1}$. As an application of this result, we show that an isolated singularity of an irreducible analytic variety of codimension $d$ in $\bC^{n+d+1}$ is uniquely determined up to affine linear transformations by the local CR geometry at a point of its Milnor link.

math.CV↗