This video covers incidence graphs, a concept from hypergraph theory, with many examples. We go over the basic properties of incidence graphs, as well as discuss how they relate to the idea of dual hypergraphs. An incidence graph is a bipartite graph representation of a hypergraph. If you are interested in learning more, here are some resources:
What is Graph Theory? This video introduces you to graph theory. It will give you an overview of what it is. Graph theory is a branch of mathematics within discrete math that is not only super fun to study for its own sake, but also incredibly useful in disciplines such as network analysis and network science, medicine, computer science, and engineering. Graphs can be used to represent networks of people, computers, and abstract relationships. Graph theory is about pairwise relationships (edges) between objects (vertices).
Our graph theory introduction will teach you about the diameter, distance, and degree of graphs and some different types of graphs. At the end of the video, I will present a challenge that I found fascinating involving the graph theory concepts from earlier in the video. I invite you to post your favorite graph in the comments and to discuss graph theory with each other.
Let me know if you have any questions or suggestions, and have an awesome day!
Reddit: https://www.reddit.com/r/Vitalsine/
Discord: https://discord.gg/dvpXxBy
Some links for additional discovery:
Centrality and Graph Theory (one of the most important uses of graph theory!):
https://www.youtube.com/watch?v=HFP4Br7uvYo
https://en.wikipedia.org/wiki/Graph_theory#:~:text=In%20mathematics%2C%20graph%20theory%20is,also%20called%20links%20or%20lines).
http://discrete.openmathbooks.org/dmoi2/ch_graphtheory.html
http://www.openproblemgarden.org/category/graph_theory
http://dimacs.rutgers.edu/~hochberg/undopen/graphtheory/graphtheory.html
...
https://www.youtube.com/watch?v=N_tJo3XwY-M
What is Centrality? This video will introduce you to centrality and give you an overview of what it is and where it used in the real world.
Betweenness centrality, closeness centrality, and degree centrality are covered in this video. This video is all about measuring the importance of nodes in a graph using centrality indices. This is also the second video in the discrete mathematics series and the first video about graph theory on the channel.
Why does centrality matter? Because networks are everywhere, and centrality gives us crucial information about networks. Ever wonder how websites are ranked? Centrality is highly relevant to many sciences and is an interesting mathematical concept in and of itself.
I encourage you to talk about centrality in the comments and to devise algorithms to determine centrality as well as debate the drawback (or benefit) that different centrality measures can identify different nodes as being "most important."
Thank you so much for watching. Have fun thinking about math!
If you enjoyed the video, please consider watching my other videos in the graph theory series:
https://www.youtube.com/playlist?list=PLZ2xtht8y2-Jx8hxFvnFQfEej1PzqFbVX
Reddit: https://www.reddit.com/r/Vitalsine/
Discord: https://discord.gg/dvpXxBy
...
https://www.youtube.com/watch?v=HFP4Br7uvYo
This video explains how to un-do the simplex graph operation. Given a simplex graph, can we recover the structure of the original graph? In this video we look at one algorithm to do so, using visual examples. We will also briefly discuss some applications of this algorithm.
Recommended Books:
*************** Hypergraph Theory **************
"Hypergraph Theory: An Introduction": https://amzn.to/43bC8h1
"Introduction to Graph and Hypergraph Theory": https://amzn.to/3Ij9Poz
******************************** Graph Theory ********************************
"Introduction to Graph Theory (Trudeau)": https://amzn.to/43e2gHR
"Graph Theory (Diestel)": https://amzn.to/3OuLxfw
"The Fascinating World of Graph Theory": https://amzn.to/3pSUFQB
*************** Misc. Undergraduate Mathematics *****************
Discrete Mathematics with Applications (Epp): https://amzn.to/3MBXzkL
A Book of Abstract Algebra (Pinter): https://amzn.to/3On2jgp
Language, Proof and Logic: https://amzn.to/3Oi68n6
Linear Algebra and Its Applications: https://amzn.to/3MhvM91
All the Math You Missed: https://amzn.to/42FqOK5
...
https://www.youtube.com/watch?v=Apu0KJNyoPo
This video covers strong hypergraph colorings. We will go over several examples, as well as draw several connections to graph theory, including to graph squares and distance-2 colorings. We also discuss applications to communication networks.
Communication Network Application Resources:
https://www.ru.is/faculty/mmh/papers/strongcol.pdf
https://link.springer.com/chapter/10.1007/978-3-540-75520-3_46
https://link.springer.com/book/10.1007/978-3-319-60469-5
Recommended Books:
******************************** Hypergraph Theory ********************************
"Hypergraph Theory: An Introduction": https://amzn.to/43bC8h1
"Introduction to Graph and Hypergraph Theory": https://amzn.to/3Ij9Poz
******************************** Graph Theory ********************************
"Introduction to Graph Theory (Trudeau)": https://amzn.to/43e2gHR
"Graph Theory (Diestel)": https://amzn.to/3OuLxfw
"The Fascinating World of Graph Theory": https://amzn.to/3pSUFQB
******************************** Misc. Undergraduate Mathematics ********************************
Discrete Mathematics with Applications (Epp): https://amzn.to/3MBXzkL
A Book of Abstract Algebra (Pinter): https://amzn.to/3On2jgp
Language, Proof and Logic: https://amzn.to/3Oi68n6
Linear Algebra and Its Applications: https://amzn.to/3MhvM91
All the Math You Missed: https://amzn.to/42FqOK5
These are my Amazon Affiliate links. As an Amazon Associate I may earn commisions for purchases made through the links above.
0:00 Definition
1:05 Strong Chromatic Number
2:30 Distance-2 Colorings and Graph Squares
5:55 Applications
#hypergraph
#hypergraphs
#vitalsine
...
https://www.youtube.com/watch?v=2uz9CNHM1dQ
This video introduces clique complexes, a type of abstract simplicial complex. We will cover several examples and special cases of clique complexes. We'll go over the relationship between clique complexes and conformal hypergraphs, as well as certain requirements that clique complexes must satisfy. This video will also introduce independence complexes. Both independence complexes and clique complexes are abstract simplicial complexes that are built from a simple graph.
...
https://www.youtube.com/watch?v=Aoh4haV7Ekc
Regular polygon areas are given a new perspective in this video through a geometry problem: the shrinking sides problem. In this problem, you start with a triangle with sides of length 1, and decrease the side lengths by some factor as you add additional sides to your shape. The question is: Does the sum of our shapes' areas go to infinity? Is our sum a convergent series or a divergent series? To solve the shrinking sides problem, we will use the concepts of limits, infinite sums, trigonometry, and geometry. In doing so, we will discover a beautiful connection between geometry and calculus.
Reddit: https://www.reddit.com/r/Vitalsine/
Discord: https://discord.gg/dvpXxBy
Note: This is a re-do of my original video to make it clearer and more rigorous.
#geometry
...
https://www.youtube.com/watch?v=kRQ3JbbeevE
This video explains clique graphs, an operation from graph theory that outputs a graph relating the maximal cliques of the input graph. The clique graph of an undirected graph G, is itself a graph with one vertex for each maximal clique in G, and in which two vertices are adjacent when their corresponding maximal cliques in G share at least one vertex. In this video you'll see examples of clique graphs, and you'll also learn some of the properties of clique graphs. One of my favorite properties is the last one covered in the video, which we'll have to prove in a future video. It's about what happens when you iterate the clique graph operation.
Here are some links for more information:
https://www.wikiwand.com/en/Clique_graph
https://www.sciencedirect.com/science/article/pii/0095895671900700?via%3Dihub
https://www.sciencedirect.com/science/article/pii/0012365X9290270P
https://www.math.cinvestav.mx/accota/ACCOTA/ACCOTA98-11.pdf
Thanks for watching!
...
https://www.youtube.com/watch?v=kvbCDu4giAY
This video introduces Generalized Mycielskians with visual examples. We will look at the generalized Mycielskian from two perspectives: the "cone over a graph," or "cone construction" as defined by Tardif in 2001 using graph products, and the generalized Mycielskian outlined by Lin et. al in 2006 using only set operations (with slight variations in notation for pedagogical purposes). The latter generalizes the Mycielskian for graphs with isolated vertices and is equivalent to the former when the graphs do not have isolated vertices.
The generalized Mycielskian, or m-Mycielskian of a graph G without isolated vertices is the tensor product of a path graph of length m with graph G. The m-Mycielskians can be used to construct graphs of arbitrarily high chromatic number and odd girth, much like the Mycielskian (the m = 2 case of the m-Mycielskians) can be used to construct graphs of arbitrarily high chromatic number.
For more information, see these links:
https://en.wikipedia.org/wiki/Mycielskian
https://www.sciencedirect.com/science/article/pii/S0166218X05003550?via%3Dihub
https://onlinelibrary.wiley.com/doi/abs/10.1002/jgt.1025
...
https://www.youtube.com/watch?v=26OrNA2VZfo
This video introduces the modular product of graphs, along with 3 visual examples. We will analyze 2 interesting properties of the modular product as well, one with respect to complementation and the other to subgraph isomorphisms of the factor graphs. The modular product of graphs is a graph product based on the cartesian product, where the vertex set is the cartesian product of the vertex sets of the factor graphs, and the edge set is produced through 2 "adjacency rules" or requirements for adjacency. The modular product has been used to transform problems of induced subgraph isomorphism to problems of finding cliques or maximum cliques in graphs.
For more information, see these links:
https://en.wikipedia.org/wiki/Modular_product_of_graphs
https://www.sciencedirect.com/science/article/abs/pii/0020019076900491?via%3Dihub
https://link.springer.com/article/10.1007%2FBF02575586
...
https://www.youtube.com/watch?v=I_-PzbUUSCo