- #246
Lawrence B. Crowell
- 190
- 2
Tony Smith said:rntsai asked "how?" is "GF(4) is the Dynkin diagram for the Lie Algebra D_4 = spin(8)".
I might not do as good a job as Lawrence B Crowell would do,
here is my attempt at showing "how?":
The Galois field GF(4) = {0,1,w,w^2}
where
w = (1/2)( - 1 + sqrt(3) i )
and
w^2 = (1/2)( - 1 - sqrt(3) i )
Look at the 0 as the zero or origin as the central dot of the D_4 Dynkin diagram visualized as being in the complex plane centered on the origin
*
\
*--* ( I used two -- to make the length more nearly equal to that of \ and / )
/
*
and
look at the 1 as the outer Dynkin dot on the right-hand side
and
look at the w as the upper outer Dynkin dot on the left-had side
and
look at the w^2 as the lower outer Dynkin dot on the left-hand side.
Tony Smith
You got it perfectly, and in this way higher Galois fields are cyclotomic elements which are Coxeter-Dynkin diagrams for various groups. In this case it is just the nice pretty triangular pattern on the argand plane. The Galois field GF(9) gives a unit element and 8-elements which are one "oct-layer," and since GF(9) = Z(i)/3Z(i), and GF(9)xGF(9) =
Z(z)/3Z(z) there are two other "layers" which define the {3, 4, 3} polytope or 24-cell. The fun goes on from there.
Lawrence B. Crowell
Lawrence B. Crowell