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A Brouwer homeomorphism is a fixed-point free, orientation-preserving homeomorphism of the plane. A foundational result of Le Calvez establishes that every such homeomorphism $f$ admits an oriented planar foliation $\mathcal{F}$ such that…

Dynamical Systems · Mathematics 2025-10-21 Nelson Schuback

We use the homotopy Brouwer theory of Handel to define a Poincar{\'e} index between two orbits for an orientation preserving fixed point free homeomorphism of the plane. Furthermore, we prove that this index is almost additive.

Dynamical Systems · Mathematics 2015-10-14 Frédéric Le Roux

We present the solution of a longstanding internal problem of noncommutative geometry, namely the computation of the index of a transversally elliptic operator on an arbitrary foliation. The new and crucial ingredient is a certain Hopf…

Differential Geometry · Mathematics 2009-10-31 Alain Connes , Henri Moscovici

In this paper we study the relationship of the Brouwer degree of a vector field with the dynamics of the induced flow. Analogous relations are studied for the index of a vector field. We obtain new forms of the Poincar% \'{e}-Hopf theorem…

Dynamical Systems · Mathematics 2024-01-17 Héctor Barge , José M. R. Sanjurjo

Brouwer homeomorphisms are fixed-point-free, orientation-preserving homeomorphisms of the plane. In recent years, their dynamics have been mostly studied through two complementary approaches, one introduced by Handel and the other by Le…

Dynamical Systems · Mathematics 2025-12-09 Nelson Schuback

We state and prove a generalization of the Poincar\'e-Hopf index theorem for manifolds with boundary. We then apply this result to non-vanishing complex vector fields.

Differential Geometry · Mathematics 2009-09-21 Benoît Jubin

Given a proper, cocompact action of a Lie groupoid, we define a higher index pairing between invariant elliptic differential operators and smooth groupoid cohomology classes. We prove a cohomological index formula for this pairing by…

Differential Geometry · Mathematics 2014-06-06 M. J. Pflaum , H. Posthuma , X. Tang

The aim of the present manuscript is to develop an index theory for singular Lagrangian systems, with a particular focus on the important class of singular operators given by Bessel type differential operators. The main motivation is to…

Dynamical Systems · Mathematics 2025-11-12 Xijun Hu , Alessandro Portaluri , Li Wu

The radial index of a 1-form on a singular set is a generalization of the classical Poincar\'e-Hopf index. We consider different classes of closed semi-analytic sets in R^n that contain 0 in their singular locus and we relate the radial…

Algebraic Geometry · Mathematics 2017-05-24 Nicolas Dutertre

We provide a coarse version of the relative index of Gromov and Lawson and thoroughly establish all of its basic properties. As an application, we discuss a general procedure to construct wrong way maps on the $K$-theory of the Roe algebra…

K-Theory and Homology · Mathematics 2025-06-18 Alexander Engel , Christopher Wulff

We pursue the study of local index theory for operators of Fourier-integral type associated to non-proper and non-isometric actions of Lie groupoids, initiated in a previous work. We introduce the notion of geometric cocycles for Lie…

K-Theory and Homology · Mathematics 2016-12-14 Denis Perrot

In this survey one discusses the notion of the Poincar\'e series of multi-index filtrations, an alternative approach to the definition, a method of computation of the Poincar\'e series based on the notion of integration with respect to the…

Algebraic Geometry · Mathematics 2015-04-21 A. Campillo , F. Delgado , S. M. Gusein-Zade

We compute (algebraically) the Euler characteristic of a complex of sheaves with constructible cohomology. A stratified Poincar\'e-Hopf formula is then a consequence of the smooth Poincar\'e-Hopf theorem and of additivity of the…

Algebraic Topology · Mathematics 2009-05-29 Stéphane Simon

In 1912 Brouwer published his translation theorem, which implies, for example, that an orientation preserving homeomorphism of the plane having a periodic point also has a fixed point. This theorem has given rise to a number of…

Dynamical Systems · Mathematics 2020-02-07 Pierre-Antoine Guiheneuf

We explore the relation between the Hopf algebra associated to the renormalization of QFT and the Hopf algebra associated to the NCG computations of transverse index theory for foliations.

High Energy Physics - Theory · Physics 2009-10-31 Alain Connes , Dirk Kreimer

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

We consider 1-forms on, so called, essentially isolated determinantal singularities (a natural generalization of isolated ones), show how to define analogues of the Poincar\'e--Hopf index for them, and describe relations between these…

Algebraic Geometry · Mathematics 2008-06-03 W. Ebeling , S. M. Gusein-Zade

When the index bundle of a longitudinal Dirac type operator is transversely smooth, we define its Chern character in Haefliger cohomology and relate it to the Chern character of the $K-$theory index. This result gives a concrete connection…

Geometric Topology · Mathematics 2007-05-23 Moulay Benameur , James Heitsch

Attractor-repeller decompositions of isolated invariant sets give rise to so-called connecting homomorphisms. These homomorphisms reveal information on the existence and structure of connecting trajectories of the underlying dynamical…

Dynamical Systems · Mathematics 2018-01-11 Axel Jänig

This paper studies homeomorphisms of surfaces isotopic to the identity by means of purely topological methods and Brouwer theory. The main development is a novel theory of orbit forcing using maximal isotopies and transverse foliations.…

Dynamical Systems · Mathematics 2017-11-09 Patrice Le Calvez , Fabio Armando Tal
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