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Total rigidity of generic quadratic vector fields  [PDF]
Yulij Ilyashenko,Vadims Moldavskis
Mathematics , 2010,
Abstract: We consider a class of foliations on the complex projective plane that are determined by a quadratic vector field in a fixed affine neighborhood. Such foliations, as a rule, have an invariant line at infinity. Two foliations with singularities on $\mathbb C P^2$ are topologically equivalent provided that there exists a homeomorphism of the projective plane onto itself that preserves orientation both on the leaves and in $\mathbb C P^2$ and brings the leaves of the first foliation to that of the second one. We prove that a generic foliation of this class may be topologically equivalent to but a finite number of foliations of the same class, modulo affine equivalence. This property is called \emph{total rigidity}. Recent result of Lins Neto implies that the finite number above does not exceed 240. This is the first of the two closely related papers. It deals with the rigidity properties of quadratic foliations, whilst the second one studies the foliations of higher degree.
Topological rigidity for holomorphic foliations  [PDF]
Mahdi Teymuri Garakani
Mathematics , 2007,
Abstract: We study analytic deformations and unfoldings of holomorphic foliations in complex projective plane $\mathbb{C}P(2)$. Let $\{\mathcal{F}_t\}_{t \in \mathbb{D}_{\epsilon}}$ be topological trivial (in $\mathbb{C}^2$) analytic deformation of a foliation $\mathcal{F}_0$ on $\mathbb{C}^2$. We show that under some dynamical restriction on $\mathcal{F}_0$, we have two possibilities: $\mathcal{F}_0$ is a Darboux (logarithmic) foliation, or $\{\mathcal{F}_t\}_{t \in \mathbb{D}_{\epsilon}}$ is an unfolding. We obtain in this way a link between the analytical classification of the unfolding and the one of its germs at the singularities on the infinity line. Also we prove that a finitely generated subgroup of $\mathrm{Diff}(\mathbb{C}^n,0)$ with polynomial growth is solvable.
Foliations with degenerate Gauss maps on $\mathbb P^4$  [PDF]
Thiago Fassarella
Mathematics , 2008,
Abstract: We obtain a classification of codimension one holomorphic foliations on $\mathbb P^4$ with degenerate Gauss maps.
Commuting holonomies and rigidity of holomorphic foliations  [PDF]
Hossein Movasati,Isao Nakai
Mathematics , 2008, DOI: 10.1112/blms/bdn029
Abstract: In this article we study deformations of a holomorphic foliation with a generic non-rational first integral in the complex plane. We consider two vanishing cycles in a regular fiber of the first integral with a non-zero self intersection and with vanishing paths which intersect each other only at their start points. It is proved that if the deformed holonomies of such vanishing cycles commute then the deformed foliation has also a first integral. Our result generalizes a similar result of Ilyashenko on the rigidity of holomorphic foliations with a persistent center singularity. The main tools of the proof are Picard-Lefschetz theory and the theory of iterated integrals for such deformations.
Stability of Holomorphic Foliations with Split Tangent Sheaf  [PDF]
Fernando Cukierman,Jorge Vitorio Pereira
Mathematics , 2005, DOI: 10.1353/ajm.2008.0011
Abstract: We show that the set of singular holomorphic foliations of the projective spaces with split tangent sheaf and with good singular set is open in the space of holomorphic foliations. As applications we present a generalization of a result by Camacho-Lins Neto about linear pull-back foliations, we give a criterium for the rigidity of $\mathcal L$-foliations of codimension $k \ge 2$ and prove a conjecture by Cerveau-Deserti about the rigidity of a codimension one $\mathcal L$-foliation of $\mathbb P^4$. These results allow us to exhibit some previously unknown irreducible components of the spaces of singular holomorphic foliations.
Partial hyperbolicity and foliations in $\mathbb{T}^3$  [PDF]
Rafael Potrie
Mathematics , 2012,
Abstract: We prove that dynamical coherence is an open and closed property in the space of partially hyperbolic diffeomorphisms of $\mathbb{T}^3$ isotopic to Anosov. Moreover, we prove that strong partially hyperbolic diffeomorphisms of $\mathbb{T}^3$ are either dynamically coherent or have an invariant two-dimensional torus which is either contracting or repelling. We develop for this end some general results on codimension one foliations which may be of independent interest.
Dynamics of quadratic polynomials II: rigidity  [PDF]
Mikhail Lyubich
Mathematics , 1995,
Abstract: This is a continuation of the series of notes on the dynamics of quadratic polynomials. We show the following Rigidity Theorem: Any combinatorial class contains at most one quadratic polynomial satisfying the secondary limbs condition with a-priori bounds. As a corollary, such maps are combinatorially and topologically rigid, and as a consequence, the Mandelbrot set is locally connected at the correspoinding parameter values.
Principal Mean Curvature Foliations on Surfaces immersed in ${\mathbb R} ^4$  [PDF]
R. Garcia,L. F. Mello,J. Sotomayor
Mathematics , 2003,
Abstract: Here are studied qualitative properties of the families of curves --foliations-- on a surface immersed in ${\mathbb R}^4$, along which it bends extremally in the direction of the mean normal curvature vector. Typical singularities and cycles are described, which provide sufficient conditions, likely to be also necessary, for the structural stability of the configuration of such foliations and their singularities, under small $C^3$ perturbations of the immersion. The conditions are expressed in terms of Darbouxian type of the normal and umbilic singularities, the hyperbolicity of cycles, and the asymptotic behavior of singularity separatrices and other typical curves of the foliations. They extend those given by Gutierrez and Sotomayor in 1982 for principal foliations and umbilic points of surfaces immersed in ${\mathbb R}^3$. Expressions for the Darbouxian conditions and for the hyperbolicity, calculable in terms of the derivatives of the immersion at singularities and cycles, are provided. The connection of the present extension from ${\mathbb R}^3$ to ${\mathbb R}^4$to other pertinent ones as well as some problems left open in this paper are proposed at the end.
Codimension one holomorphic foliations on $\mathbb P^n_{\mathbb C}$: problems in complex geometry  [PDF]
Dominique Cerveau
Mathematics , 2012,
Abstract: After a short review on foliations, we prove that a codimension 1 holomorphic foliation on $\mathbb P^3_{\mathbb C}$ with simple singularities is given by a closed rational 1-form. The proof uses Hironaka-Matsumura prolongation theorem of formal objects.
Rigidity of Riemannian foliations with complex leaves on Kaehler manifolds  [PDF]
Paul-Andi Nagy
Mathematics , 2002,
Abstract: We study Riemannian foliations with complex leaves on Kaehler manifolds. The tensor T, the obstruction to the foliation be totally geodesic, is interpreted as a holomorphic section of a certain vector bundle. This enables us to give classification results when the manifold is compact.
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