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Abstract separation systems provide a simple general framework in which both tree-shape and high cohesion of many combinatorial structures can be expressed, and their duality proved. Applications range from tangle-type duality and tree…

Combinatorics · Mathematics 2017-04-19 Reinhard Diestel

The notion of $\mathcal{H}$-treewidth, where $\mathcal{H}$ is a hereditary graph class, was recently introduced as a generalization of the treewidth of an undirected graph. Roughly speaking, a graph of $\mathcal{H}$-treewidth at most $k$…

Data Structures and Algorithms · Computer Science 2023-06-30 Bart M. P. Jansen , Jari J. H. de Kroon , Michal Wlodarczyk

We introduce and analyze parallelizable algorithms to compress and accurately reconstruct finite simplicial complexes that have non-trivial automorphisms. The compressed data -- called a complex of groups -- amounts to a functor from (the…

Group Theory · Mathematics 2020-04-21 Lisa Carbone , Vidit Nanda , Yusra Naqvi

It is folklore that tree-width is monotone under taking subgraphs (i.e. injective graph homomorphisms) and contractions (certain kinds of surjective graph homomorphisms). However, although tree-width is obviously not monotone under any…

Combinatorics · Mathematics 2025-06-11 Benjamin Merlin Bumpus , James Fairbanks , Will J. Turner

Counting the number of answers to conjunctive queries is a fundamental problem in databases that, under standard assumptions, does not have an efficient solution. The issue is inherently #P-hard, extending even to classes of acyclic…

Databases · Computer Science 2024-09-12 Hubie Chen , Gianluigi Greco , Stefan Mengel , Francesco Scarcello

Chordal and factor-width decomposition methods for semidefinite programming and polynomial optimization have recently enabled the analysis and control of large-scale linear systems and medium-scale nonlinear systems. Chordal decomposition…

Optimization and Control · Mathematics 2021-11-23 Yang Zheng , Giovanni Fantuzzi , Antonis Papachristodoulou

An extension of order theory is presented that serves as a formalism for the study of dendroidal sets analogously to way the formalism of order theory is used in the study of simplicial sets.

Algebraic Topology · Mathematics 2012-01-20 Ittay Weiss

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

This paper presents a precursory yet novel approach to the question answering task using structural decomposition. Our system first generates linguistic structures such as syntactic and semantic trees from text, decomposes them into…

Computation and Language · Computer Science 2016-04-05 Tomasz Jurczyk , Jinho D. Choi

Complex systems are usually represented as an intricate set of relations between their components forming a complex graph or network. The understanding of their functioning and emergent properties are strongly related to their structural…

Data Analysis, Statistics and Probability · Physics 2014-01-08 Sergio Gomez , Alberto Fernandez , Clara Granell , Alex Arenas

We introduce a formalism based on a combinatorial notion of cell complex subject to an inclusion-reversing duality operation. Our main goal is to open the way for a functorial definition of field theories in a context where no manifold or…

Mathematical Physics · Physics 2022-04-15 Maxime Savoy

Taking a Feynman categorical perspective, several key aspects of the geometry of surfaces are deduced from combinatorial constructions with graphs. This provides a direct route from combinatorics of graphs to string topology operations via…

Algebraic Topology · Mathematics 2022-01-26 Clemens Berger , Ralph M. Kaufmann

We describe a basic correspondence between linear algebraic structures within vector embeddings in artificial neural networks and conditional independence constraints on the probability distributions modeled by these networks. Our framework…

Machine Learning · Computer Science 2024-07-15 Matthew Trager , Alessandro Achille , Pramuditha Perera , Luca Zancato , Stefano Soatto

Single-image 3D shape reconstruction is an important and long-standing problem in computer vision. A plethora of existing works is constantly pushing the state-of-the-art performance in the deep learning era. However, there remains a much…

Computer Vision and Pattern Recognition · Computer Science 2021-04-23 Songfang Han , Jiayuan Gu , Kaichun Mo , Li Yi , Siyu Hu , Xuejin Chen , Hao Su

A new general decomposition theory inspired from modular graph decomposition is presented. This helps unifying modular decomposition on different structures, including (but not restricted to) graphs. Moreover, even in the case of graphs,…

Data Structures and Algorithms · Computer Science 2007-11-20 Binh-Minh Bui-Xuan , Michel Habib , Vincent Limouzy , Fabien De Montgolfier

We introduce a theory for encoding and manipulating algebraic data on categories via $\textit{concentration structures}$, which are equivalence relations on morphisms that satisfy certain axioms. For any category with a concentration…

Category Theory · Mathematics 2025-10-10 Yangxiao Luo , Shunyu Wan

Tree sets are posets with additional structure that generalize tree-like objects in graphs, matroids, or other combinatorial structures. They are a special class of abstract separation systems. We study infinite tree sets and how they…

Combinatorics · Mathematics 2025-05-16 Jay Lilian Kneip

Modelling musical structure is vital yet challenging for artificial intelligence systems that generate symbolic music compositions. This literature review dissects the evolution of techniques for incorporating coherent structure, from…

Sound · Computer Science 2024-03-14 Keshav Bhandari , Simon Colton

Parameterized complexity seeks to use input structure to obtain faster algorithms for NP-hard problems. This has been most successful for graphs of low treewidth: Many problems admit fast algorithms relative to treewidth and many of them…

Computational Complexity · Computer Science 2022-12-20 Falko Hegerfeld , Stefan Kratsch

We construct the ordinary irreducible representations of the group of automorphisms of a finite rooted tree and we get a natural parametrization of them. To achieve this goals, we introduce and study the combinatorics of tree compositions,…

Representation Theory · Mathematics 2025-04-15 Fabio Scarabotti