Rotations of 4-Cubes

663 Views Asked by At

I have recently learned the orbit stabilizer theorem, and have encountered unexpected results pertaining to the rotations of a tesseract; I am curious if there is any intuition for this.

A $4$-Cube has $(16*4)/2 = 32$ edges using some simple counting, and has $24*8 = 192$ rotational symmetries, which I obtained by considering that each of the $8$ cubical 'faces' can map to any other in $24$ ways (each way is a rotational symmetry of a 3-cube). Each edge has all $32$ edges in its orbit, and so by orbit stabilizer we conclude each edge has $192/32 = 6$ stabilizing rotations.

This seems very bizarre to me, as it suggest that you can perform $3$ rotations of a $4$-cube that keep any edge in the same position, facing the same direction, so essentially nothing has changed. Does this mean it is possible to rotate a $4$-cube non-trivially in $2$ ways while keeping one edge completely fixed? Or does the edge have to move, only to end up exactly as it was when it began?

Is my reasoning correct, and is there any intuitive way to understand these results? In general, are rotation in higher dimensions too bizarre to have an intuitive grasp of, and are there some interesting things I should know about these rotations? Thanks!

1

There are 1 best solutions below

3
On BEST ANSWER

If you examine a tesseract, you should be able to find three cubical hyperfaces that meet at a single edge. In fact, every edge has three hyperfaces arranged symmetrically around it in this fashion.

While keeping this edge fixed, then, you can rotate one of the three adjoining cubical hyperfaces onto one of the others. Repeat this rotation to find the second non-trivial rotation that leaves this edge fixed. The third repetition takes the hyperface back to its original position.