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We define two types of local indices of a vector field at an isolated zero on the boundary, and prove Poincare-Hopf-type index theorems for certain vector fields on a compact smooth manifold which have only isolated zeros.

Geometric Topology · Mathematics 2008-03-20 Hiroaki Kamae , Masayuki Yamasaki

We describe several families of Lagrangian submanifolds in the complex Euclidean space which are H-minimal, i.e. critical points of the volume functional restricted to Hamiltonian variations. We make use of various constructions involving…

Differential Geometry · Mathematics 2010-08-17 Henri Anciaux , Ildefonso Castro

Indices of singular points of a vector field or of a 1-form on a smooth manifold are closely related with the Euler characteristic through the classical Poincar\'e--Hopf theorem. Generalized Euler characteristics (additive topological…

Geometric Topology · Mathematics 2019-03-19 S. M. Gusein-Zade

A short proof of the Caratheodory conjecture about index of an isolated umbilic on the convex 2-dimensional sphere is suggested. The argument is based on the study of geodesic lines near cone-type singularity of a metric induced by…

Differential Geometry · Mathematics 2009-01-23 Igor Nikolaev

We consider the problem of minimal volume vector fields on a given Riemann surface, specialising on the case of $M^\star$, that is, the arbitrary radius 2-sphere with two antipodal points removed. We discuss the homology theory of the unit…

Differential Geometry · Mathematics 2023-07-20 Rui Albuquerque

Theorems on the existence of vector fields with given sets of Indexes of isolated Singular points are proved for the cases of closed manifolds, pairs of manifolds, manifolds with boundary, and gradient fields. It is proved that, on a…

Dynamical Systems · Mathematics 2007-05-23 A. O. Prishlyak

We impose constraints on the odd coordinates of super Teichm\"uller space in the uniformization picture for the monodromies around Ramond punctures, thus reducing the overall odd dimension to be compatible with that of the moduli spaces of…

Geometric Topology · Mathematics 2019-11-06 Ivan C. H. Ip , Robert C. Penner , Anton M. Zeitlin

This article is devoted to the generalization of results obtained in 2002 by Jabin, Otto and Perthame. In their article they proved that planar vector fields taking value into the unit sphere of the euclidean norm and satisfying a given…

Analysis of PDEs · Mathematics 2017-01-12 Pierre Bochard , Paul Pegon

In this article, we study the generalized Poincare problem from the opposite perspective, by establishing lower bounds on the degree of the vector field in terms of invariants of the variety.

Commutative Algebra · Mathematics 2024-03-18 Marc Chardin , S. Hamid Hassanzadeh , Claudia Polini , Aron Simis , Bernd Ulrich

We prove, under suitable conditions, a lower bound on the number of pinned distances determined by small subsets of two-dimensional vector spaces over fields. For finite subsets of the Euclidean plane we prove an upper bound for their…

Combinatorics · Mathematics 2020-12-16 Ben Lund , Giorgis Petridis

The set of primitive vectors on large spheres in the euclidean space of dimension d>2 equidistribute when projected on the unit sphere. We consider here a refinement of this problem concerning the direction of the vector together with the…

Number Theory · Mathematics 2017-05-17 Menny Aka , Manfred Einsiedler , Uri Shapira

Let $\alpha\in\r$ and let $\vec{v}\in\r^3$ be a unit vector. A singular minimal surface $\Sigma$ in Euclidean space is a surface $\Sigma$ whose mean curvature $H$ satisfies $H=\alpha\frac{\langle N,\vec{v}\rangle}{\langle…

Differential Geometry · Mathematics 2025-07-21 Rafael López

A celebrated theorem of Hadwiger states that the Euler-Poincar\'e characteristic is the the unique invariant and continuous valuation on the distributive lattice of compact polyhedra in R^n that assigns value one to each convex non-empty…

Metric Geometry · Mathematics 2012-09-17 Andrea Pedrini

This paper introduces a submanifold of the moduli space of unitary representations of the fundamental group of a punctured sphere with fixed local monodromy. The submanifold is defined via products of involutions through Lagrangian…

Geometric Topology · Mathematics 2007-05-23 Elisha Falbel , Richard A. Wentworth

For a punctured surface $S$, we characterize the representations of its fundamental group into $\mathrm{PSL}_2 (\mathbb{C})$ that arise as the monodromy of a meromorphic projective structure on $S$ with poles of order at most two and no…

Geometric Topology · Mathematics 2021-09-17 Subhojoy Gupta

We characterize all logarithmic, holomorphic vector-valued modular forms which can be analytically continued to a region strictly larger than the upper half-plane.

Number Theory · Mathematics 2011-01-26 Marvin Knopp , Geoffrey Mason

The stability of the 3-dimensional Hopf vector field, as a harmonic section of the unit tangent bundle, is viewed from a number of different angles. The spectrum of the vertical Jacobi operator is computed, and compared with that of the…

Differential Geometry · Mathematics 2009-10-31 A. Higuchi , B. S. Kay , C. M. Wood

We prove essentially optimal bounds for norms of spectral projectors on thin spherical shells for the Laplacian on the cylinder (R/Z)*R. In contrast to previous investigations into spectral projectors on tori, having one unbounded dimension…

Classical Analysis and ODEs · Mathematics 2022-12-16 Pierre Germain , Simon L. Rydin Myerson

We study certain points significant for the hyperbolic geometry of the unit disk. We give explicit formulas for the intersection points of the Euclidean lines and the stereographic projections of great circles of the Riemann sphere passing…

Metric Geometry · Mathematics 2024-07-08 Masayo Fujimura , Oona Rainio , Matti Vuorinen

We give a new proof of the well-known result that the minimal volume vector fields on $\mathbb{S}^3(r)$ are the Hopf vector fields. Such proof relies again on calibration theory, arising here from a systematic point of view given by a…

Differential Geometry · Mathematics 2025-10-17 Rui Albuquerque