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Let us be given two graphs $\Gamma_1$, $\Gamma_2$ of $n$ vertices. Are they isomorphic? If they are, the set of isomorphisms from $\Gamma_1$ to $\Gamma_2$ can be identified with a coset $H\cdot\pi$ inside the symmetric group on $n$…

Group Theory · Mathematics 2017-10-13 Harald Andrés Helfgott , Jitendra Bajpai , Daniele Dona

We give an isomorphism test that runs in time $n^{\operatorname{polylog}(h)}$ on all $n$-vertex graphs excluding some $h$-vertex vertex graph as a topological subgraph. Previous results state that isomorphism for such graphs can be tested…

Data Structures and Algorithms · Computer Science 2025-04-21 Daniel Neuen

Parameterized complexity theory has enabled a refined classification of the difficulty of NP-hard optimization problems on graphs with respect to key structural properties, and so to a better understanding of their true difficulties. More…

Data Structures and Algorithms · Computer Science 2017-10-19 David Coudert , Guillaume Ducoffe , Alexandru Popa

In this paper, we present two main results. First, by only one conjecture (Conjecture 2.9) for recognizing a vertex symmetric graph, which is the hardest task for our problem, we construct an algorithm for finding an isomorphism between two…

Data Structures and Algorithms · Computer Science 2017-06-29 Caishi Fang

In the past decades for more and more graph classes the Graph Isomorphism Problem was shown to be solvable in polynomial time. An interesting family of graph classes arises from intersection graphs of geometric objects. In this work we show…

Data Structures and Algorithms · Computer Science 2016-06-23 Daniel Neuen

In 1996, Bodlaender showed the celebrated result that an optimal tree decomposition of a graph of bounded treewidth can be found in linear time. The algorithm is based on an algorithm of Bodlaender and Kloks that computes an optimal tree…

Data Structures and Algorithms · Computer Science 2020-03-19 Ernst Althaus , Sarah Ziegler

We claimed that there is a polynomial algorithm to test if two graphs are isomorphic. But the algorithm is wrong. It only tests if the adjacency matrices of two graphs have the same eigenvalues. There is a counterexample of two…

Computational Complexity · Computer Science 2022-10-18 Reiner Czerwinski

An explicit algorithm is presented for testing whether two non-directed graphs are isomorphic or not. It is shown that for a graph of n vertices, the number of n independent operations needed for the test is polynomial in n. A proof that…

Data Structures and Algorithms · Computer Science 2007-05-23 Moshe Schwartz

It's important to design polynomial time algorithms to test if two graphs are isomorphic at least for some special classes of graphs. An approach to this was presented by Eugene M. Luks(1981) in the work \textit{Isomorphism of Graphs of…

Discrete Mathematics · Computer Science 2012-09-06 Adria Alcala Mena

The group isomorphism problem asks whether two finite groups given by their Cayley tables are isomorphic or not. Although there are polynomial-time algorithms for some specific group classes, the best known algorithm for testing isomorphism…

Group Theory · Mathematics 2026-03-10 Saveliy V. Skresanov

In this paper we consider the problem of testing whether a graph has bounded arboricity. The family of graphs with bounded arboricity includes, among others, bounded-degree graphs, all minor-closed graph classes (e.g. planar graphs, graphs…

Data Structures and Algorithms · Computer Science 2021-04-28 Talya Eden , Reut Levi , Dana Ron

In this paper we present an algorithm, called conauto-2.0, that can efficiently compute a set of generators of the automorphism group of a graph, and test whether two graphs are isomorphic, finding an isomorphism if they are. This algorithm…

Data Structures and Algorithms · Computer Science 2011-08-05 José Luis López-Presa , Antonio Fernández Anta , Luis Núñez Chiroque

A polynomial algorithm for graphs' isomorphism testing is constructed in assumption that there exists a corresponding polynomial algorithm for graphs with trivial automorphism group.

Combinatorics · Mathematics 2007-05-23 Aleksandr Golubchik

The AHU-algorithm solves the computationally difficult graph isomorphism problem for rooted trees, and does so with a linear time complexity. Although the AHU-algorithm has remained state of the art for almost 50 years, it has been…

Computational Complexity · Computer Science 2024-01-17 Anna Lindeberg

It is confirmed in this work that the graph isomorphism can be tested in polynomial time, which resolves a longstanding problem in the theory of computation. The contributions are in three phases as follows. 1. A description graph…

Computational Complexity · Computer Science 2023-01-25 Rui Xue

Branchwidth determines how graphs, and more generally, arbitrary connectivity (basically symmetric and submodular) functions could be decomposed into a tree-like structure by specific cuts. We develop a general framework for designing…

Data Structures and Algorithms · Computer Science 2021-11-08 Fedor V. Fomin , Tuukka Korhonen

In recent years, we have seen several approaches to the graph isomorphism problem based on "generic" mathematical programming or algebraic (Gr\"obner basis) techniques. For most of these, lower bounds have been established. In fact, it has…

Computational Complexity · Computer Science 2016-07-18 Christoph Berkholz , Martin Grohe

Graph polynomials encode fundamental combinatorial invariants of graphs. Their computation is investigated using tree and path decomposition frameworks, with formal definitions of treewidth, k-trees, and pathwidth establishing the…

Discrete Mathematics · Computer Science 2025-09-29 Mehul Bafna , Shaghik Amirian

A commonly studied means of parameterizing graph problems is the deletion distance from triviality (Guo et al. 2004), which counts vertices that need to be deleted from a graph to place it in some class for which efficient algorithms are…

Data Structures and Algorithms · Computer Science 2014-10-17 Jannis Bulian , Anuj Dawar

The group isomorphism problem in computational complexity asks whether two finite groups given by their Cayley tables are isomorphic or not. Although polynomial-time isomorphism tests exist for many specific types of groups, no general…

Group Theory · Mathematics 2026-05-27 Saveliy V. Skresanov