Monthly Archives: July 2013

Lovász conjecture and Devil’s algorithm

A graph is vertex-transitive if its group of automorphisms acts transitively on the set of vertices. For example, the skeletons of uniform polyhedral are all vertex-transitive, as is the complete graph Kn. It’s obvious that a vertex-transitive graph must be … Continue reading

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Coxeter groups and beyond

Some polyhedra have lots of symmetries. For example, consider the omnitruncated dodecahedron: The interactive demonstration constructs it kaleidoscopically, by reflecting a fundamental region (the Schwarz triangle) in three mirrors. The same fundamental region, however, can result in lots of different polyhedra and … Continue reading

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Cipher 34: Manual

Many of my ciphers were computerised. By contrast, this one was created manually and could have appeared 400 years ago, long before Blaise Pascal produced the first mechanical calculator.

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