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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, topological-graph-theory, random-graphs, graph-colorings and several others.

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The terminology for a node's number of in-links in weighted directed graph

The quantity you are asking about is usually called the "fan-in" of node $i$. The dual quantity which counts the number of nodes to which $i$ points is called the "fan-out". The terms are standard at …
Vidit Nanda's user avatar
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2 votes
2 answers
651 views

Finding a vertex equidistant from two given vertices in a digraph

The question is essentially in the title: while attempting to compute the colimit of a diagram of cell complexes, my colleague and I find ourselves stumped with the following graph theoretic problem: …
Vidit Nanda's user avatar
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1 vote

different way of selecting a random graph

There are at least two instances that I can recall where such graphs have been studied. As you've remarked, in general too much depends on the base graph, so you're only going to get somewhere by rest …
Vidit Nanda's user avatar
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3 votes

Is this graph known?

I think you just have the complement of a line graph here. Start with $K_n$, the complete directed graph on $n$ vertices (including self-edges). That is, the vertex set is $\lbrace 1,\ldots,n \rbrace …
Vidit Nanda's user avatar
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4 votes

Graph of graph homomorphisms

Warning: the following statement answers an older version of this question. Let $G$ be the graph you want to realize. Then, $\text{Hom}(\bullet,G) \simeq G$ where $\bullet$ is the graph containing on …
Vidit Nanda's user avatar
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3 votes
0 answers
57 views

Algorithm to construct metric space endomorphism with controlled square

Given a finite metric space $(M,d)$ with parameters $K \geq 1$ and $\epsilon > 0$, I'd like to algorithmically check for the existence of a non-identity map $\phi:M \to M$ which happens to be $K$-biLi …
Vidit Nanda's user avatar
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2 votes

Recovering a Weighted Graph from Shortest Path Distances

Andreas Blass has produced a simple counterexample to (A) in his answer. I suspect that if your graph is flat in the sense of Andrew Stacey's answer here, then you can in fact recover it from the pair …
Vidit Nanda's user avatar
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4 votes
Accepted

Pairs of paths with the same source and target

Pairs of paths with the same source and target but with no other nodes in common are called parallel paths, at least on the computer science side of things in graph theory -- you can google the term t …
Vidit Nanda's user avatar
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5 votes
3 answers
305 views

Tracking automorphism groups of graph processes

Start with an edgeless graph on $n$ labeled vertices, and note that the automorphism group is $\Sigma_n$, the symmetric group on $n$ elements. Now imagine that we randomly start throwing in all of the …
Vidit Nanda's user avatar
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6 votes
0 answers
172 views

Uniformly sampling from the set of all simplicial maps

Let $K$ and $L$ be finite simplicial complexes that remain fixed throughout. How does one efficiently sample (according to the uniform distribution) elements from the finite set of simplicial map …
Vidit Nanda's user avatar
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