# Spin product of graphs

1. Aug 7, 2012

### LagrangeEuler

Last edited: Aug 7, 2012
2. Aug 8, 2012

### matematikuvol

No. You have sum.
So
Spins may take values +1 or -1. Because of that
result of
$$S_iS_jS_jS_k$$
is either +1 or -1.
For example
$$\sum_{S_1=-1,1}\sum_{S_2=-1,1}S_iS_{i+1}=-1 \cdot (-1)+(-1)\cdot 1+1\cdot(-1)+1-1 \cdot (-1)+(-1)\cdot 1+1\cdot(-1)=0$$
I don't know what that means in the graph case. If someone knows it would me nice to write down.