Graph theory is the study of graphs, mathematical structures used to model pairwise relations between objects.

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6
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1answer
90 views

On bandwidth of graphs

I am trying to find references on algorithms for graphs of bounded bandwidth, in the same way as it is done with treewidth for instance. I could only find research related to computing the bandwidth, ...
4
votes
0answers
45 views

Graph Isomorphism of Strongly Regular Graph with fixed parameter

$G, H$ are strongly regular graphs with parameter $(n, r, \lambda, \mu)$ where $\lambda$ is constant. Here, $n$ is the number of total vertices. Each graph is $r$ regular. Every two adjacent ...
5
votes
1answer
108 views

Maximum common subgraph of two planar graphs of bounded degree k

Given two planar graphs of bounded degree (i.e. each node has no more than D edges), I'd like to find their maximum common subgraph. I know that the more general problem applied to maximal planar ...
0
votes
1answer
50 views

Cycle cover for structured graph

Consider the undirected graph $G=(V,E)$ example below. More precisely, the vertices in $V$ are labelled with $(x,y)$-coordinates and there is an edge between every vertices sharing the same $x$ and ...
3
votes
1answer
208 views

The maximum number of induced cycles in a simple directed graph

Is the maximum number of induced circuits in a simple directed graph known? I tried the family of graphs suggested by David and the number of induced cycles is seems to be exactly $3^{n/3} + ...
8
votes
1answer
133 views

3-color a cubic graph such that a MIS receives only two colors

According to Brooks'_theorem, a cubic graph (3-regular graph) containing no $K_4$ can be properly colored by three colors. (Such a color can actually be found in linear time, which is not our primary ...
8
votes
1answer
116 views

Label-disjoint paths in directed graphs

Checking if there are two edge-disjoint paths from $s$ to $t$ in a given undirected graph $G$ is in P via a standard solution based on maxflow. I am interested in the complexity of the following ...
0
votes
0answers
87 views

Confusion about the text of the NP-complete and P treewidth problems [closed]

I am confused about the text of the two classes of treewidth problems one of which is in NP-complete and the other is in P. Let me first quote them from Treewidth, partial k-trees, and chordal ...
1
vote
1answer
97 views

Max network flow with arbitrary source / sink

I'm wondering: given a fixed graph G, if we're to calculate the max flow between the vertices s and t, how different is the problem to calculate the max flow between the vertices s' and t, or ...
1
vote
0answers
64 views

Percolation probabilities

I have a finite undirected graph with a probability $p_e$ given for each edge $e$. This gives a random graph by removing each edge e with probability $1-p_e$ independently of the others. I'm ...
-2
votes
0answers
42 views

Clustering of a signed graph

A signed graph is a graph in which edges are labeled as positives or negatives. First task is to form $k$ number of clusters of signed graph such as to maximize total number of positive links inside ...
5
votes
0answers
94 views

Vertex Disjoint Path Covers of Hypercube-Like Graphs

This is a followup question relating to an older question I posted, namely: Decomposing the n-cube into vertex-disjoint paths. Given a graph $G = (V, E)$ and sets of distinct vertices $S = \{s_1, ...
7
votes
1answer
190 views

Problem of graph bi-partition (related to graph isomorphism)

I am considering the following problem: Input: 3 graphs $G=(V,E)$, $H_1$, $H_2$ Question: Is there some $V_1\subseteq V$ such that $G[V_1]$ (the subgraph induced by $V_1$) is isomorphic to ...
0
votes
1answer
73 views

Max-sum graph-partition for maximizing intra-edge weights?

I would like to know if the following problem has already been studied, and if so how is it called. In particular I'm interested in approximability results. Input: A graph G with negative or ...
7
votes
1answer
225 views

Is the proceedings of WG 2015 published?

Within theoretical computer science, the "Workshop on Graph-Theoretic Concepts in Computer Science (WG)" is one of the main specialized venues for publication of papers dealing with graph theory. It's ...
1
vote
0answers
51 views

About complexity of recovering or learning Bayesian networks

Are there complexity theoretic results about recoverability or learnability of the marginals (of the source vertices) and the conditionals (along each of the edges) of a Bayesian network from having ...
4
votes
1answer
219 views

Enumerating all (super)orientations of an undirected graph

Given an undirected graph $G$, an orientation of $G$ is a directed graph obtained by assigning every edge a direction, a superorientation of $G$ is a directed graph obtained by orienting every edge in ...
4
votes
0answers
76 views

Graph partition with weighted vertices and edges

I am searching for an algorithm to apply to a specific graph partition problem that I am interested in. It feels like a topic that people from CS may have worked on but it is also different from ...
7
votes
0answers
111 views

Kleinberg Rubinfeld Short Paths in Expander Graphs for Hypergraphs

In the 1996 paper "Short Paths in Expander Graphs" by Kleinberg and Rubinfeld, the authors show a randomized polynomial-time algorithm for finding an embedding of a graph $H$ into a graph $G$, if $G$ ...
5
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0answers
138 views

Machine learning algorithms on hypergrap models

Graphical models are a very useful tool with many applications, whereby a joint distribution of a set of random variables is modeled using only pairwise dependencies between the variables, and two ...
8
votes
1answer
119 views

Tree-decomposition with clique interfaces

Let $G=(V,E)$ be a finite undirected graph. A tree decomposition $(T,\lambda)$ of $G$ is a tree $T$ with labeling function $\lambda : T \to 2^{V}$ such that: For every edge $\{v_1,v_2\} \in E$, ...
2
votes
1answer
115 views

Partition into triangles in a 3-partite graphe

Let $G=(X\cup Y\cup Z,E)$ be a 3-partite graph such that: $|X|=|Y|=|Z|=q$. $2 \leq d(v) \leq 6$ for all $v \in X\cup Y\cup Z$, where $d(v)$ is the degree of v. $\sum_{x \in X} d(x)=\sum_{y \in ...
6
votes
1answer
107 views

What is the complexity of vertex cover on k-partite graphs?

Given a k-partite graph which is already partitioned into k parts, what is the complexity of finding a vertex cover of minimum size? I guess that it's NP-hard, but couldn't yet prove it or find ...
-5
votes
1answer
88 views

What is the complexity of the fastest method of k-coloring any graph? [closed]

I heard brute-force is the only method. Is there any other way? Is there a way to prove that the complexity cannot be exponential?
8
votes
1answer
144 views

Complexity of the edge-disjoint cycle covers

I am interested in decompositions of a directed graph $G=(V,E)$ into non-intersecting Eulerian subgraphs $G_i=(V_i, E_i)$. I want to find the decomposition that covers the largest number of edges. I ...
3
votes
1answer
385 views

Construction of a Global Isomorphism(permutation) for Graph Isomorphism using Local Isomorphism

Given two graphs $G, H$ (each has $n$ vertices). We, split $G$ into subgraphs $G_1, G_2... G_x$ (total $x$ vertex set). Similarly,assume $H$ has subgraphs $H_1, H_2... H_x$ (total $x$ vertex set). ...
2
votes
1answer
102 views

Converting a pictorial representation of a directed graph to a adjacency matrix

I am not sure if there is a better forum to ask this question, so I will try here. Consider an image, say in .jpeg format, representing a directed graph, with nodes. Is there an algorithm, be it a ...
0
votes
0answers
20 views

Optimization of process duration when multiple processes interact

When you have a process composed of multiple steps (e.g., a recipe), where: each step S has a specific duration d(S) steps ...
10
votes
1answer
191 views

Complexity of digraph homomorphism to an oriented cycle

Given a fixed directed graph (digraph) $D$, the $D$-COLORING decision problem asks whether an input digraph $G$ has a homomorphism to $D$. (A homomorphism of $G$ to $D$ is a mapping $f$ of $V(G)$ to ...
5
votes
0answers
230 views

Maximizing the number of selected edges with opposing requirements

Consider the following problem: Input: a complete bipartite graph $G$ with its edges colored either white or black, a number $k$. Output: a subset of vertices $W$ of size $k$ which maximizes the ...
9
votes
0answers
308 views

Upper Bound on Number of $n \times n$ Boolean matrices of Boolean rank at most $k$

An $n \times n$ Boolean matrix $B$ has Boolean rank $k$ if there exist matrices $L \in \{0,1\}^{n \times k}$ and $R \in \{0,1\}^{k \times n}$, s.t. $B = L \circ R$. Here $\circ$ denotes the Boolean ...
6
votes
2answers
227 views

Local Graph Isomorphism to construct Global Graph Isomorphism

Does there exist a Graph Isomorphism Algorithm that uses Local Isomorphism to construct a Global Isomorphism? For example, two graphs are given, say, $H, G$. it is asked to determine whether $G\simeq ...
8
votes
1answer
140 views

Classes of graphs with superconstant treewidth

There are several interesting classes of graphs with bounded treewidth. For instance, trees (treewidth 1), series parallel graphs (treewidth 2), outerplanar graphs (treewidth 2), $k$-outerplanar ...
1
vote
1answer
129 views

Graph class with easy chromatic number, but NP-hard coloring

Is there a graph class for which the chromatic number can be computed in polynomial time, but finding an actual $k$-coloring with $k=\chi(G)$ is NP-hard? Without any further restriction the answer ...
7
votes
0answers
155 views

Is there a special name for the following type of graphs?

Weighted graphs such that if $x$ and $y$ are nodes in the graph, and $p$ and $p'$ are two paths in the graph between $x$ and $y$, then the weight of $p$ equals the weight of $p'$.
5
votes
2answers
168 views

The relationship between degree of vertex and size of dominating set

I was wondering is there any relationship between degree of vertex and size of dominating set. For example, if I know the number of vertices is $n$, and I could know each vertex in the graph has ...
0
votes
0answers
87 views

How to efficiently generate a random 0-1 matrix of a given rank

How to efficiently generate a random $n\!\times\!n$ $0$-$1$ matrix of rank $k<n$?
7
votes
1answer
169 views

Complexity of a graph-rewriting problem

I recently came across the following problem which seems to fall in the context of graph rewriting problems: Input: A graph $G=(V,E)$ with maximum degree 3, an edge $e_0 \in E$ and pairs of graphs ...
5
votes
1answer
194 views

Canonical way of coloring graphs (individualization) for isomorphism purpose

Stefan Kratsch and Pascal Schweitzer in their paper Graph Isomorphism for Graph Classes Characterized by two Forbidden Induced Subgraphs give a characterization of graphs on which Graph Isomorphism ...
20
votes
1answer
255 views

Minor closed properties that are explicitly MSO expressible

Below, MSO denotes the monadic second order logic of graphs with vertex-set and edge-set quantifications. Let $\mathcal{F}$ be a minor closed family of graphs. It follows from Robertson and ...
1
vote
0answers
49 views

Optimal distribution of integer edge weights

I am not sure whether the following problem has been studied. Any help would be greatly appreciated. I have $L$ sets, $S_1, S_2,...,S_L$, each of $n$ elements, taken from a universe of $N$ elements. ...
3
votes
1answer
128 views

Does such model exists?

I have a problem on distributed graph, with the following model: 1. There is a Global Graph $G=(V,E)$ 2. There are $k$ computers. 3. Each computer $1 \leq i \leq k$ knows ALL the nodes of the ...
3
votes
2answers
181 views

Generate connected induced subgraphs as the satisfying assignments to a SAT instance

I want a SAT instance (in CNF) whose set of satisfying assignments are the connected induced subgraphs of a given input graph. A general solution would be helpful, but I really only need this when the ...
0
votes
1answer
99 views

Fractional but not integer multi-commodity minimum cost flow

I'm searching for an example digraph for the multi-commodity minimum cost flow problem with integer demand. There shouldn't be an integer but fractional optimal solution. I found here a similar ...
0
votes
0answers
82 views

Find max weight induced graph in a multipartite graph with one vertex from each part

Consider the follow problem: Input: $G=(V,E)$, a weighted $k$-partite graph with $n$ vertices. Output: $U \subseteq V$, one vertex from each part, maximizing the total weight of the induced graph ...
-4
votes
1answer
177 views

Is graph isomorphism still open for bounded clique width or bounded rank width? 2015 paper claims it is polynomial [closed]

To my knowledge, graph isomorphism for graphs with bounded clique width or bounded rank width is open. 2015 arxiv paper claims it is polynomial: Isomorphism Testing for Graphs of Bounded Rank Width ...
4
votes
2answers
200 views

Partition graph into 2 or more claw-free subgraphs

Is it NP-hard to partition the vertex set of graph G into k subsets so that they induce k claw-free subgraphs of G?
7
votes
1answer
674 views

Probability of two vertices being connected by some path in a random directed graph

Define $G(n, p)$ as a random directed graph ($n$ vertices; we put edge between two vertices with probability $p$). What are the known results for the following problem: Fix two vertices $v$ and ...
3
votes
0answers
78 views

Embedding distortion under group quotient

The high level question is as follows: Suppose some group (here assumed to be a vector space of $\mathbf{F}_2^n$) has a low-distortion embedding into $l_1$. Under what condition does the quotient of ...
3
votes
5answers
385 views

How to constrain a finite automaton (NFA and DFA) to a tree?

I have a finite automaton by the standard model Hopcroft & Ullman define: $$ M = (Q, \Sigma, \delta, q_0, F) $$ Where $\delta$ is the transition function mapping $Q \times \Sigma \mapsto Q$, such ...