# Tagged Questions

Questions about the branch of combinatorics called graph theory (not to be used for questions concerning the graph of a function). This tag can be further specialized via using it in combination with more specialized tags such as extremal-graph-theory, spectral-graph-theory, algebraic-graph-theory, ...

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### Removing cycles in a directed graph by swapping edges orientation

I have the following problem: let $G$ be a finite directed graph with $V$ vertices $v_i$ and $E$ (directed) edges $e_j$. I know that if an edge $e_k = (v_i, v_j)$ is in the graph, then the opposite ...
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### A measurement for vertex- and edge failure sensitivity

I want to have a metric that helps me judge how independent different paths in one graph are. So here are my assumptions: A graph consists of a set of vertices ($V$) and edges ($E$). A path ...
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### On symmetric difference of $k$-partite perfect matchings

Suppose we have a bipartite graph we know that symmetric difference of any two perfect matchings is union of even cycles. Conversely when is it true that every union of even cycles comes from ...
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### Tree decompositions in linear hypergraphs

A linear hypergraph is a pair $\pi=(X, L)$ where $X\neq \emptyset$ is a finite set and $L\subseteq {\cal P}(X)$ has the following properties: for $e\in L$ we have $|e|\geq 2$; if $e_1\neq e_2 \in L$ ...
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### Tree-chromatic number and Hadwiger number

Let $G=(V,E)$ be a finite, simple, undirected graph. For any set $X$ we set $[X]^2 := \big\{\{x,y\}: x\neq y \in X\big\}$. If $T$ is a tree, then a map $W: V(T)\to {\cal P}(V(G))$ is called a tree-...
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### All pairs shortest path with maximum distance

I didn't succeed to find an algorithm that finds the shortest path in a weighted non directed graph between all pairs of nodes whose shortest path distance are inferior to a specific number. I think ...
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### Good graph theory and combinatorics book

I am looking for a book about graph theory and combinatorics. I am studying the routing problem in communication networks, therefore my interest is on a book with a wide set of problems and examples. ...
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### Convex polyhedra, combinatorial types and Symmetry

Steinitz theorem says that combinatorial types of convex polyhedra is identified with 3-connected planar graph, called by a polyhedral graph. A symmetry of polyhedral graph means that a vertex ...
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