Validity of Direct Product Structure of Symmetry Group

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SUMMARY

The symmetry group of a regular octahedron is isomorphic to the direct product Z2⊗Z2⊗Z2⊗S3, as established in "Groups, Graphs and Trees." This structure arises from grouping the octahedron's vertices into three categories: front-back, top-bottom, and left-right, with permutations represented by the S3 factor. The application of a symmetry from this direct product to a vertex involves a sequence of transformations akin to navigating three-dimensional coordinates. The group elements are defined as geometric transformations that map the octahedron onto itself, with specific operations yielding the identity transformation.

PREREQUISITES
  • Understanding of group theory, specifically direct products and isomorphisms.
  • Familiarity with geometric transformations and their representations in symmetry groups.
  • Knowledge of permutation groups, particularly S3 and its applications.
  • Basic grasp of tensor products in the context of algebraic structures.
NEXT STEPS
  • Study the properties of direct products in group theory.
  • Explore the geometric interpretations of symmetry groups in three-dimensional objects.
  • Investigate the role of permutation groups in combinatorial structures.
  • Learn about the application of tensor products in algebraic topology and group theory.
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Mathematicians, particularly those specializing in group theory and geometry, as well as students and researchers interested in the structural properties of symmetry groups and their applications in various mathematical contexts.

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In short, if we consider the group of symmetries of a regular octahedron, we see (or at least, the author of "Groups, Graphs and Trees" saw...) that the group is isomoprhic to Z2\otimesZ2\otimesZ2\otimesS3 - particularly since if we break up the vertices into 3 groups of front-back, top-bottom and left-right we get the first three factors and the second factor is obtained by further permutation. But my question is how does an element of a direct product act on an element of a graph? If we take a vertex v in the graph, since all symmetries commute here, if we apply a symmetry h in the direct product to v, we are thus applying 4 symmetries each in one of the factors of the direct product. So is the vertex taken to "coordinates" of whatever the direct product indicates similar to the way we consider 3 dimensional coordinates as in if we have the coordinates (1,2,3) we could move 2 in the y direction then 1 in the x and 3 in the z or 3 in the z direction THEN 2 in the y then 1 in the x etc. and thus the same process for the location of the vertex v after h is applied. Thanks in advance for your help - I know I probably rambled a bit...
 
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A direct product is written with ##\times## or ##oplus## for additionally written groups. ##\otimes## notes the tensor product. Anyway. You number the vertices of the octahedron and observe how group elements permute them. The group elements are defined as the geometric transformations which turn the octahedron onto itself, e.g. an upside down transformation. Then we have several reflection planes etc. The structure is defined by the way they form another transformation by consecutive application of two. E.g. upside down applied twice is the identity. It is a candidate for one copy of ##\mathbb{Z}_2##. In general it is not so easy to determine the group structure by its multiplication table. However, geometric figures are relatively simple. Let us assume all such transformations can be written as a product of three different involutions and a ##3-##cycle: ##T=I_1I_2I_3C##.
In case of a direct product, we get the structure by ##TT'=(I_1I_2I_3C)(I'_1I'_2I'_3C')=I_1I'_1I_2I'_2I_3I'_3CC'##. So we have to check, whether this is true for all the transformations.
 

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