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Every expanding map on a closed manifold is topologically conjugate to an expanding map on an infra-nilmanifold, but not every infra-nilmanifold admits an expanding map. In this article we give a complete algebraic characterization of the…

Dynamical Systems · Mathematics 2014-07-31 Karel Dekimpe , Jonas Deré

We propose a model of the functional architecture of curvature sensible cells in the visual cortex that associates curvature with scale. The feature space of orientation and position is naturally enhanced via its oriented prolongation,…

Neurons and Cognition · Quantitative Biology 2025-04-24 Vasiliki Liontou

H. Hertz called any manifold M with a given nonintegrable distribution {\it nonholonomic}. Vershik and Gershkovich stated and R. Montgomery proved that the space of germs of any nonholonomic distribution on M with an open and dense orbit of…

Representation Theory · Mathematics 2007-05-23 Pavel Grozman , Dimitry Leites , Irina Shchepochkina

Recently there has been renewed interest among differential geometers in the theory of Engel structures. We introduce holomorphic analogues of these structures, and pose the problem of classifying projective manifolds admitting them.…

Algebraic Geometry · Mathematics 2014-07-23 Francisco Presas , Luis Eduardo Sola Conde

We study pairs of Engel structures on four-manifolds whose intersection has constant rank one and which define the same even contact structure, but induce different orientations on it. We establish a correspondence between such pairs of…

Dynamical Systems · Mathematics 2019-10-09 D. Kotschick , T. Vogel

We develop a topological framework for Engel expansions that treats both directions of the correspondence between points of $(0,1]$ and nondecreasing digit sequences. We endow the sequence space with the product topology to study the…

Dynamical Systems · Mathematics 2025-10-14 Min Woong Ahn

Round fold maps are smooth maps on closed manifolds which are locally represented as the product maps of Morse functions and identity maps on open disks and whose singularity is realized as concentrically embedded spheres. The author…

Algebraic Topology · Mathematics 2022-07-21 Naoki Kitazawa

Fold maps are smooth maps at each singular point of which it is represented as the product map of a Morse function and the identity map. Round fold maps are, in short, such maps the sets of all singular points of which are embedded…

Algebraic Topology · Mathematics 2023-01-18 Naoki Kitazawa

A map on a surface whose automorphism group has a subgroup acting regularly on its vertices is called a Cayley map. Here we generalize that notion to maniplexes and polytopes. We define $\mathcal{M}$ to be a \emph{Cayley extension} of…

Combinatorics · Mathematics 2023-05-22 Gabe Cunningham , Elías Mochán , Antonio Montero

For any Engel 4-fold, we show that the scanning map from the space of Engel knots to the space of formal Engel knots is a weak homotopy equivalence when restricted to the complement of the orbits of the Engel kernel. This is a relative,…

Geometric Topology · Mathematics 2017-10-31 Roger Casals , Álvaro del Pino

We give two applications of the 2-Engel relation, classically studied in finite and Lie groups, to the 4-dimensional topological surgery conjecture. The A-B slice problem, a reformulation of the surgery conjecture for free groups, is shown…

Geometric Topology · Mathematics 2018-07-30 Michael Freedman , Vyacheslav Krushkal

A compact 4-dimensional manifold is a non-singular graph-manifold if it can be obtained by the glueing T^2-bundles over compact surfaces (with boundary) of negative Euler characteristics. If none of glueing diffeomorphisms respect the…

Geometric Topology · Mathematics 2014-10-01 A. Mozgova

A map is a connected topological graph $\Gamma$ cellularly embedded in a surface. In this paper, applying Tutte's algebraic representation of map, new ideas for enumerating non-equivalent orientable or non-orientable maps of graph are…

General Mathematics · Mathematics 2009-09-29 Linfan Mao , Yanpei Liu

A manifold $M^n$ inherits a labeled $n$-dimensional graph $\widetilde{M}[G^L]$ structure consisting of its charts. This structure enables one to characterize fundamental groups of manifolds, classify those of locally compact manifolds with…

General Mathematics · Mathematics 2010-06-21 Linfan Mao

The monography examines the problem of constructing a group of automorphisms of a graph. A graph automorphism is a mapping of a set of vertices onto itself that preserves adjacency. The set of such automorphisms forms a vertex group of a…

History and Overview · Mathematics 2024-07-18 Sergey Kurapov , Maxim Davidovsky

In [CPPP] it was shown that Engel structures satisfy an existence $h$-principle, and the question of whether a full $h$-principle holds was left open. In this note we address the classification problem, up to Engel deformation, of Cartan…

Symplectic Geometry · Mathematics 2017-08-02 Álvaro del Pino

We call two Engel structures isotopic if they are homotopic through Engel structures by a homotopy that fixes the characteristic line field. In the present paper we define an isotopy invariant of Engel structures on oriented circle bundles…

Symplectic Geometry · Mathematics 2012-09-07 Mirko Klukas , Bijan Sahamie

A map is a connected topological graph cellularly embedded in a surface and a complete map is a cellularly embedded complete graph in a surface. In this paper, all automorphisms of complete maps of order n are determined by permutations on…

General Mathematics · Mathematics 2009-09-29 Linfan Mao , Yanpei Liu , Feng Tian

The Engel graph of a finite group $G$ is a directed graph encoding the pairs of elements in $G$ satisfying some Engel word. Recent work of Lucchini and the third author shows that, except for a few well-understood cases, the Engel graphs of…

Group Theory · Mathematics 2023-04-20 F. Dalla Volta , F. Mastrogiacomo , P. Spiga

By a map we mean a $2$-cell decomposition of a closed compact surface, i.e., an embedding of a graph such that every face is homeomorphic to an open disc. Automorphism of a map can be thought of as a permutation of the vertices which…

Combinatorics · Mathematics 2021-01-08 Ken-ichi Kawarabayashi , Bojan Mohar , Roman Nedela , Peter Zeman