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Information about Königsberg, Euler and the origins of graph theory

A slidecast explaining the origins of graph theory and the solution to the 7 bridges problem of Königsberg. I discuss some modern applications of graph theory too.

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History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading K¨nigsberg, East Prussia o capital of East Prussia (1457–1945) Pregel river university birth place of Immanuel Kant, David Hilbert, K¨the Kollwitz a destroyed at the end of World War II

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Nowadays: Kaliningrad Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Nowadays: Kaliningrad Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Nowadays: Kaliningrad Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Leonhard Euler Basel 1707 – St.-Petersburg 1783 professor at 20 enormously productive inﬂuence found everywhere in math and physics most famous formula: 1 + e iπ = 0 Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o The 7 bridges problem Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading The 7 bridges problem A B C D

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading The 7 bridges problem A B C Deﬁnitions graph vertices (singular: vertex) — edges order of a vertex D

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory When can you take the desired walk? 1 4 A 2 3 vertex of even order Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading When can you take the desired walk? 1 4 A 1 2 3 A 3 2 vertex of odd order vertex of even order

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading When can you take the desired walk? 1 4 A 1 2 A 3 3 2 vertex of odd order vertex of even order The graph is traversable if all vertices have even order → Euler tour, a closed walk if exactly 2 vertices have odd order → use them to start and ﬁnish your walk

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Examples of traversable graphs The graph is traversable if all vertices have even order → Euler tour, a closed walk if exactly 2 vertices have odd order → use them to start and ﬁnish your walk A 1 3 C 2 B Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading Examples of traversable graphs The graph is traversable if all vertices have even order → Euler tour, a closed walk if exactly 2 vertices have odd order → use them to start and ﬁnish your walk A 1 3 C 2 1 B 4 A 5 2 D 3 C B

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Back to the 7 bridges problem A B C D Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading Back to the 7 bridges problem the order of A is 3 A the order of B is 4 the order of C is 3 the order of D is 3 B C D

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading Back to the 7 bridges problem the order of A is 3 A the order of B is 4 the order of C is 3 the order of D is 3 B D C Conclusion The graph of the 7 bridges problem is not traversable. It’s impossible to take a walk crossing every bridge exactly once.

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Application 1: traﬃc Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Application 2: social networks Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Application 2: social networks Applications of graph theory Summary & further reading

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading Application 3: ranking of search results by Google each vertex represents a web page arrow D → A means: page D contains a link to page A

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading Summary What have you learned in this slidecast? basic concepts of graph theory: graph, vertex, edge, order of a vertex you and Euler solved the 7 bridges problem by proving when a graph is traversable the K¨nigsberg graph is not traversable o some applications of graph theory, e.g. traﬃc, social networks

History of K¨nigsberg o The 7 bridges of K¨nigsberg o Applications of graph theory Summary & further reading More information? Reinhard Diestel, Graph Theory (3rd edition), Springer Verlag, 2005 www.math.ubc.ca/~solymosi/2007/443/GraphTheoryIII.pdf Fred Buckley, A Friendly Introduction to Graph Theory, Prentice Hall, 2002 Glen Gray, Graph Theory 1 — Intro via Konigsberg Bridge www.youtube.com/watch?v=BK kYjFWWX0

A slidecast explaining the origins of graph theory and the solution to the 7 bridges problem of Königsberg. I discuss some modern applications of graph ...

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Graph Theory Origin and ... field of graph theory. He created first graph to ... to make the graph created from bridges of Königsberg, a Euler ...

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Home; Education; Königsberg, Euler and the origins of graph theory; of 25 ×

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Sharing the wonders of graph theory throughout history ... Euler and the Königsberg Bridge Problem. Hamilton and the Icosian Game. The Four Color Problem.

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Yet from such deceptively frivolous origins, graph theory has grown into a powerful and ... ‘Euler circuit’ to a modern proof of the main result of the ...

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Graph Theory /Introduction. From ... Map of Königsberg in Euler's time showing the actual ... Since the graph corresponding to historical Königsberg has ...

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The Seven Bridges of Königsberg is a ... there are five bridges in Kaliningrad that were a part of the Euler's problem. In terms of graph theory, ...

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The Königsberg bridge problem asks if the seven bridges ... and represented the beginning of graph theory. ... J. "Leonhard Euler and the Königsberg ...

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... graph theory is the study of graphs, ... Euler's formulation with ... and faces of a convex polyhedron was studied and generalized by others and is at ...

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