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We introduce the graph theoretical parameter of edge treewidth. This parameter occurs in a natural way as the tree-like analogue of cutwidth or, alternatively, as an edge-analogue of treewidth. We study the combinatorial properties of…

Discrete Mathematics · Computer Science 2021-12-15 Loïc Magne , Christophe Paul , Abhijat Sharma , Dimitrios M. Thilikos

We prove that various classical conformal diffeomorphism groups, which are known to be essential [1], are in fact properly essential. This is a consequence of a local criterion on a conformal diffeomorphism in the form of a cohomological…

Symplectic Geometry · Mathematics 2011-08-01 Stefan Müller , Peter Spaeth

We examine the metrics that arise when a finite set of points is embedded in the real line, in such a way that the distance between each pair of points is at least 1. These metrics are closely related to some other known metrics in the…

Combinatorics · Mathematics 2011-08-02 Adam N. Letchford , Hanna Seitz , Dirk Oliver Theis

This paper examines the geometry of left-invariant vector fields on five-dimensional, simply connected, nilpotent Lie groups equipped with left-invariant Riemannian metrics. Using the canonical identification between the Lie algebra and the…

Differential Geometry · Mathematics 2025-08-18 M. L. Foka , R. P. Nimpa , M. B. N. Djiadeu

In this paper, left-invariant almost contact metric structures on three-dimensional non-unimodular Lie groups are investigated. It is proved that for every Riemannian Lie group, there is one of these structures. In addition, left-invariant…

Differential Geometry · Mathematics 2020-02-12 Pejhman Vatandoost-Miandehi , A. Razavi

We investigate the combinatorial and geometric properties of automorphism groups of universal right-angled Coxeter groups, which are the automorphism groups of free products of copies of Z_2. It is currently an open question as to whether…

Group Theory · Mathematics 2019-10-31 Charles Cunningham

The class of closed graphs by a linear ordering on their sets of vertices is investigated. A recent characterization of such a class of graphs is analyzed by using tools from the proper interval graph theory.

Combinatorics · Mathematics 2015-09-23 Marilena Crupi

We describe explicit open books on arbitrary plumbings of oriented circle bundles over closed oriented surfaces. We show that, for a non-positive plumbing, the open book we construct is horizontal and the corresponding compatible contact…

Geometric Topology · Mathematics 2007-05-23 Tolga Etgü , Burak Ozbagci

We study the properties of several proximity measures for the vertices of weighted multigraphs and multidigraphs. Unlike the classical distance for the vertices of connected graphs, these proximity measures are applicable to weighted…

Combinatorics · Mathematics 2007-05-23 Pavel Chebotarev , Elena Shamis

We show that it is possible to use Bondy-Chvatal closure to design an FPT algorithm that decides whether or not it is possible to cover vertices of an input graph by at most k vertex disjoint paths in the complement of the input graph. More…

Data Structures and Algorithms · Computer Science 2016-12-16 Pavel Dvořák , Dušan Knop , Tomáš Masařík

A zigzag in a map (a $2$-cell embedding of a connected graph in a connected closed $2$-dimensional surface) is a cyclic sequence of edges satisfying the following conditions: 1) any two consecutive edges lie on the same face and have a…

Combinatorics · Mathematics 2019-04-04 Mark Pankov , Adam Tyc

We prove that holomorphic maps from an open subset of a complex smooth projective curve to a complex smooth projective rationally simply connected variety can be approximated by algebraic maps for the compact-open topology. This theorem can…

Algebraic Geometry · Mathematics 2025-08-22 Olivier Benoist , Olivier Wittenberg

In this paper, we formulate a simple algorithm that detects contours around a region of interest in an image. After an initial smoothing, the method is based on viewing an image as a topographic surface and finding convex and/or concave…

Image and Video Processing · Electrical Eng. & Systems 2019-05-31 Victor Churchill

We introduce an essential open book foliation, a refinement of the open book foliation, and develop technical estimates of the fractional Dehn twist coefficient (FDTC) of monodromies and the FDTC for closed braids, which we introduce as…

Geometric Topology · Mathematics 2015-09-02 Tetsuya Ito , Keiko Kawamuro

We extend previous results on boundedness of sets of coherent sheaves on a compact K\"ahler manifold to the relative and not necessarily smooth case. This enlarged context allows us to prove properness properties of the relative Douady…

Complex Variables · Mathematics 2022-09-22 Matei Toma

Let $X$ be a Hamiltonian vector field defined on a symplectic manifold $(M,\omega)$, $g$ a nowhere vanishing smooth function defined on an open dense subset $M^0$ of $M$. We will say that the vector field $Y = gX$ is conformally…

Symplectic Geometry · Mathematics 2011-02-22 Charles-Michel Marle

We give an answer in the "geometric" setting to a question of de Fernex, Ein, and Ishii, asking when local isomorphisms of $k$-schemes can be detected on the associated maps of local arc or jet schemes. In particular, we show that their…

Algebraic Geometry · Mathematics 2019-05-22 Devlin Mallory

We prove that any weakly symplectically fillable contact manifold is tight. Furthermore we verify the strong Weinstein conjecture for contact manifolds that appear as the concave boundary of a directed symplectic cobordism whose positive…

Symplectic Geometry · Mathematics 2025-04-29 Wolfgang Schmaltz , Stefan Suhr , Kai Zehmisch

We relate the Mather invariant of diffeomorphisms of the (closed) interval to their asymptotic distortion. For maps with only parabolic fixed points, we show that the former is trivial if and only if the latter vanishes. As a consequence,…

Dynamical Systems · Mathematics 2022-09-20 Hélène Eynard-Bontemps , Andrés Navas

We give a proof of openness of versality using coherent functors. As an application, we streamline Artin's criterion for algebraicity of a stack. We also introduce multi-step obstruction theories, employing them to produce obstruction…

Algebraic Geometry · Mathematics 2013-04-09 Jack Hall