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Let $G$ be a finite group, and let $X$ be a smooth, orientable, connected, closed 4-dimensional $G$-manifold. Let $\mathcal{S}$ be a smooth, embedded, $G$-invariant surface in $X$. We introduce the concept of a $G$-equivariant trisection of…

Geometric Topology · Mathematics 2025-01-31 Jeffrey Meier , Evan Scott

Let $G$ be an undirected graph. We say that $G$ contains a ladder of length $k$ if the $2 \times (k+1)$ grid graph is an induced subgraph of $G$ that is only connected to the rest of $G$ via its four cornerpoints. We prove that if all the…

Combinatorics · Mathematics 2024-01-31 Steven Chaplick , Steven Kelk , Ruben Meuwese , Matus Mihalak , Georgios Stamoulis

We investigate algorithms with predictions in computational geometry, specifically focusing on the basic problem of computing 2D Delaunay triangulations. Given a set $P$ of $n$ points in the plane and a triangulation $G$ that serves as a…

Computational Geometry · Computer Science 2026-01-14 Sergio Cabello , Timothy M. Chan , Panos Giannopoulos

Spanning tree modulus is a generalization of effective resistance that is closely related to graph strength and fractional arboricity. The optimal edge density associated with spanning tree modulus is known to produce two hierarchical…

Combinatorics · Mathematics 2024-07-26 Nathan Albin , Kapila Kottegoda , Pietro Poggi-Corradini

We consider the problem of uniformly generating a spanning tree, of a connected undirected graph. This process is useful to compute statistics, namely for phylogenetic trees. We describe a Markov chain for producing these trees. For cycle…

Data Structures and Algorithms · Computer Science 2020-07-08 Luís M. S. Russo , Andreia Sofia Teixeira , Alexandre P Francisco

Algorithms that decompose a manifold into simple pieces reveal the geometric and topological structure of the manifold, showing how complicated structures are constructed from simple building blocks. This note describes a way to…

Geometric Topology · Mathematics 2022-06-08 Mark Bell , Joel Hass , J. Hyam Rubinstein , Stephan Tillmann

We describe an efficient algorithm to compute a pseudotriangulation of a finite planar family of pairwise disjoint convex bodies presented by its chirotope. The design of the algorithm relies on a deepening of the theory of visibility…

Computational Geometry · Computer Science 2012-08-14 Luc Habert , Michel Pocchiola

A phylogenetic tree is a graphical representation of an evolutionary history of taxa in which the leaves correspond to the taxa and the non-leaves correspond to speciations. One of important problems in phylogenetic analysis is to assemble…

Combinatorics · Mathematics 2022-02-25 Hiroshi Hirai , Yuni Iwamasa

We prove that any triangulation of a surface different from the sphere and the projective plane admits an orientation without sinks such that every vertex has outdegree divisible by three. This confirms a conjecture of Bar\'at and Thomassen…

Combinatorics · Mathematics 2014-12-17 Boris Albar , Daniel Gonçalves , Kolja Knauer

While a considerable amount of semantic parsing approaches have employed RNN architectures for code generation tasks, there have been only few attempts to investigate the applicability of Transformers for this task. Including hierarchical…

Computation and Language · Computer Science 2022-06-28 Klaudia-Doris Thellmann , Bernhard Stadler , Ricardo Usbeck , Jens Lehmann

Tree decompositions were developed by Robertson and Seymour. Since then algorithms have been developed to solve intractable problems efficiently for graphs of bounded treewidth. In this paper we extend tree decompositions to allow cycles to…

Data Structures and Algorithms · Computer Science 2007-05-23 Melanie J. Agnew , Christopher M. Homan

Embeddings of graphs into distributions of trees that preserve distances in expectation are a cornerstone of many optimization algorithms. Unfortunately, online or dynamic algorithms which use these embeddings seem inherently randomized and…

Data Structures and Algorithms · Computer Science 2021-02-11 Bernhard Haeupler , D Ellis Hershkowitz , Goran Zuzic

We consider the problem of lossless compression of binary trees, with the aim of reducing the number of code bits needed to store or transmit such trees. A lossless grammar-based code is presented which encodes each binary tree into a…

Information Theory · Computer Science 2013-04-30 Jie Zhang , En-hui Yang , John C. Kieffer

A consensus tree is a phylogenetic tree that captures the similarity between a set of conflicting phylogenetic trees. The problem of computing a consensus tree is a major step in phylogenetic tree reconstruction. It also finds applications…

Data Structures and Algorithms · Computer Science 2017-07-05 Paweł Gawrychowski , Gad M. Landau , Wing-Kin Sung , Oren Weimann

Given two sets of points in the plane, $P$ of $n$ terminals and $S$ of $m$ Steiner points, a Steiner tree of $P$ is a tree spanning all points of $P$ and some (or none or all) points of $S$. A Steiner tree with length of longest edge…

Computational Geometry · Computer Science 2010-12-08 A. Karim Abu-Affash

In this paper, we extend the classical quadrilateral based hierarchical Poincar\'e-Steklov (HPS) framework to triangulated geometries. Traditionally, the HPS method takes as input an unstructured, high-order quadrilateral mesh and relies on…

Numerical Analysis · Mathematics 2026-01-01 Gentian Zavalani

This paper presents a new algorithm "A" for constructing Seifert surfaces from n-bridge projections of links. The algorithm produces minimal complexity surfaces for large classes of braids and alternating links. In addition, we consider a…

Geometric Topology · Mathematics 2008-02-01 Joan E. Licata

Neural networks with tree-based sentence encoders have shown better results on many downstream tasks. Most of existing tree-based encoders adopt syntactic parsing trees as the explicit structure prior. To study the effectiveness of…

Computation and Language · Computer Science 2018-08-30 Haoyue Shi , Hao Zhou , Jiaze Chen , Lei Li

We give an algorithm that for an input n-vertex graph G and integer k>0, in time 2^[O(k)]n either outputs that the treewidth of G is larger than k, or gives a tree decomposition of G of width at most 5k+4. This is the first algorithm…

Data Structures and Algorithms · Computer Science 2013-04-24 Hans Bodlaender , Pål G. Drange , Markus S. Dregi , Fedor V. Fomin , Daniel Lokshtanov , Michał Pilipczuk

We consider structure of typical gradient flows bifurcations on closed surfaces with minimal number of singular points. There are two type of such bifurcations: saddle-node (SN) and saddle connections (SC). The structure of a bifurcation is…

Dynamical Systems · Mathematics 2024-08-21 Illia Ovtsynov , Alexandr Prishlyak