Counting Faces, Edges, and Vertices of cubed 1-toroid

48 Views Asked by At

Trouble determining the Euler's characteristic on the shape below.
Here's what I counted: $G=(V,E,F) = (16,24,10)$
Shouldn't $χ$ be $0$?
1-toroid.png

1

There are 1 best solutions below

1
On BEST ANSWER

I think you have counted $(V,E,F)$ wrong.

This shape has a vertex for every single integer coordinate of a 2x4x4 grid in 3-D, so $V=32$. It has 24 edges on the top layer, and another 24 on the bottom layer, with 16 edges from top to bottom, so $E=64$. It has 8 faces on the top, 8 on the bottom, 4 on the inside hole, 12 around the outside, so $F=32$.

As you correctly predicted, $V-E+F = 32-64+32 = 0$.