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 Why is a² + b² ≥ 2ab ?
 A remark on the divergence theorem
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 On the existence of a metric compatible with a given connection
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 27 lines on a smooth cubic surface
 Weighted HsiungMinkowski formulas and rigidity of umbilic hypersurfaces
 The discrete GaussBonnet theorem
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 A functional inequality on the boundary of static manifolds
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Category Archives: Topology
The discrete GaussBonnet theorem
This is a slight extension of my previous note on discrete GaussBonnet theorem. As mentioned in that note, this is a generalization of the wellknown fact that the sum of the exterior angles of a polygon is always , which … Continue reading
Posted in Calculus, Combinatorics, Discrete Mathematics, Geometry, Topology
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Topological proof of the infinitude of primes
Perhaps everyone knows how to prove “there exist infinitely many primes” by one or more ways. Here I just want to share a proof using topology and prime factorization theorem. It is also (perhaps highly) possible that most of the … Continue reading
Posted in Number Theory, Topology
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Sum of angle defects of polyhedrons
In this short note we will discuss a generalization of the wellknown fact that the sum of the exterior angles of a polygon is always , which can also be regarded as a very special case of the GaussBonnet theorem. … Continue reading