Arithmetic proof of the multiplicity-weighted Euler characteristic for symmetrically arranged space-filling polyhedra
[ 1 ] Instytut Chemii Bioorganicznej Polskiej Akademii Nauk, Polska Akademia Nauk | [ P ] pracownik
2021
artykuł naukowy
angielski
EN The puzzling observation that the famous Euler's formula for three-dimensional polyhedra V - E + F = 2 or Euler characteristic x = V-E+F-I=1 (where V, E, F are the numbers of the bounding vertices, edges and faces, respectively, and I = 1 counts the single solid itself) when applied to space-filling solids, such as crystallographic asymmetric units or Dirichlet domains, are modified in such a way that they sum up to a value one unit smaller (i.e. to 1 or 0, respectively) is herewith given general validity. The proof provided in this paper for the modified Euler characteristic, chi(m) = V-m - E-m + F-m - I-m = 0, is divided into two parts. First, it is demonstrated for translational lattices by using a simple argument based on parity groups of integer-indexed elements of the lattice. Next, Whitehead's theorem, about the invariance of the Euler characteristic, is used to extend the argument from the unit cell to its asymmetric unit components.
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CC BY (uznanie autorstwa)
ostateczna wersja opublikowana
03.2021
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