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Harmonic morphisms between riemannian manifolds

Bent Fuglede (1978)

Annales de l'institut Fourier

A harmonic morphism f : M N between Riemannian manifolds M and N is by definition a continuous mappings which pulls back harmonic functions. It is assumed that dim M dim N , since otherwise every harmonic morphism is constant. It is shown that a harmonic morphism is the same as a harmonic mapping in the sense of Eells and Sampson with the further property of being semiconformal, that is, a conformal submersion of the points where d f vanishes. Every non-constant harmonic morphism is shown to be an open mapping....

Helicoidal surfaces in Minkowski space with constant mean curvature and constant Gauss curvature

Rafael López, Esma Demir (2014)

Open Mathematics

We classify all helicoidal non-degenerate surfaces in Minkowski space with constant mean curvature whose generating curve is a the graph of a polynomial or a Lorentzian circle. In the first case, we prove that the degree of the polynomial is 0 or 1 and that the surface is ruled. If the generating curve is a Lorentzian circle, we prove that the only possibility is that the axis is spacelike and the center of the circle lies on the axis.

Higher order contact of real curves in a real hyperquadric. II

Yuli Villarroel (1998)

Archivum Mathematicum

Let Φ be an Hermitian quadratic form, of maximal rank and index ( n , 1 ) , defined over a complex ( n + 1 ) vector space V . Consider the real hyperquadric defined in the complex projective space P n V by Q = { [ ς ] P n V , Φ ( ς ) = 0 } . Let G be the subgroup of the special linear group which leaves Q invariant and D the ( 2 n ) - distribution defined by the Cauchy Riemann structure induced over Q . We study the real regular curves of constant type in Q , tangent to D , finding a complete system of analytic invariants for two curves to be locally equivalent...

Higher order Schwarzian derivatives in interval dynamics

O. Kozlovski, D. Sands (2009)

Fundamenta Mathematicae

We introduce an infinite sequence of higher order Schwarzian derivatives closely related to the theory of monotone matrix functions. We generalize the classical Koebe lemma to maps with positive Schwarzian derivatives up to some order, obtaining control over derivatives of high order. For a large class of multimodal interval maps we show that all inverse branches of first return maps to sufficiently small neighbourhoods of critical values have their higher order Schwarzian derivatives positive up...

Higher symmetries of the Laplacian via quantization

Jean-Philippe Michel (2014)

Annales de l’institut Fourier

We develop a new approach, based on quantization methods, to study higher symmetries of invariant differential operators. We focus here on conformally invariant powers of the Laplacian over a conformally flat manifold and recover results of Eastwood, Leistner, Gover and Šilhan. In particular, conformally equivariant quantization establishes a correspondence between the algebra of Hamiltonian symmetries of the null geodesic flow and the algebra of higher symmetries of the conformal Laplacian. Combined...

Holomorphic Cartan geometries and rational curves

Indranil Biswas, Benjamin McKay (2016)

Complex Manifolds

We prove that any compact Kähler manifold bearing a holomorphic Cartan geometry contains a rational curve just when the Cartan geometry is inherited from a holomorphic Cartan geometry on a lower dimensional compact Kähler manifold. This shows that many complex manifolds admit no or few holomorphic Cartan geometries.

Homogénéité locale pour les métriques riemanniennes holomorphes en dimension 3

Sorin Dumitrescu (2007)

Annales de l’institut Fourier

Une métrique riemannienne holomorphe sur une variété complexe M est une section holomorphe q du fibré S 2 ( T * M ) des formes quadratiques complexes sur l’espace tangent holomorphe à M telle que, en tout point m de M , la forme quadratique complexe q ( m ) est non dégénérée (de rang maximal, égal à la dimension complexe de M ). Il s’agit de l’analogue, dans le contexte holomorphe, d’une métrique riemannienne (réelle). Contrairement au cas réel, l’existence d’une telle métrique sur une variété complexe compacte n’est...

Homogeneous Cartan geometries

Matthias Hammerl (2007)

Archivum Mathematicum

We describe invariant principal and Cartan connections on homogeneous principal bundles and show how to calculate the curvature and the holonomy; in the case of an invariant Cartan connection we give a formula for the infinitesimal automorphisms. The main result of this paper is that the above calculations are purely algorithmic. As an example of an homogeneous parabolic geometry we treat a conformal structure on the product of two spheres.

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