[next] [prev] [up] Date: Tue, 28 Dec 93 00:43:02 +0100
[next] [prev] [up] From: Dik T. Winter <Dik.Winter@cwi.nl >
~~~ [prev] [up] Subject: Re: Group theory basics (Re: Symmetry)

One additional remark:

>Well, if P is a rotation operator, you could perform a rotation
>two ways. I guess one is pre-multiplication and one is

1)  For i = 1 to 24  B(i) = A(P(i))

I would write this as B = P A, and say that A is premultiplied by P,
or equivalently that P is postmultiplied by A.

There is quite a bit of confusion about this. When permutation
groups are considered; even text-books do not agree. When A and P
are permutations you can find both that P A means: apply P first, A next,
but also: apply A first, P next. (The first meaning comes from the pure
group theorists, the second meaning more from the algebra inclined.)

Sorry to confuse the issue, but when I read such texts I have always to
think hard to get at the intended meaning. I think the functional
notation is much clearer and leads to less confusion.

Of course, doing notations for cube rotations the group theorists
notation is applied, but when doing abstract operations...

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