Tuesday, 29 July 2008

gt.geometric topology - Simplicial and cubical decompositions of low valence

Every surface can be triangulated in such a way that at most 7 trianlges meet at one vertex. Every surface can be decomposed in squares such that at every vertex at most 5 suqares meet. For surfaces of genus more than 1 this is the low bound.



What happen in higher dimensions, for example for 3 and 4-manifolds, ect...? It should be easy to show that for every dimension n there are numbers S(n) and and C(n) such that every manifold Mn admits a simplicial decomposition with at most S(n)
simplexes at every vertex and a cubical decomposition with at most C(n) cubes at every vertex. The refference of Gil below confirms this for n=3.



Here are three questions (I suspect they are hard).



1) Can it be proven that C(n)>2n?



2) Can it be proven that S(n)>fracVol(Sn)Vol(Deltan), where Deltan is the spherical tetrahedron with edge of length fracpi3 in the unit sphere Sn.



3) Is there any reasonable estimation for C(n) and S(n) from above?

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