[next] [prev] [up] Date: Sat, 05 Nov 94 22:16:00 -0500
[next] [prev] [up] From: Mark Longridge <mark.longridge@canrem.com >
[next] ~~~ [up] Subject: Shifty Invariance
Even more thoughts on "Shift Invariance"

>>Mark continues
>>    Equivalent to (U1 R1)^35= (R1 U1)^35 & Shift Invariant
>>    UR11 = U2 R1 U1 R1 U1 R3 U1 R3 U1 R3 U2 R1 U1 R1 U1 R3 U1 R3 U1 R3
>>           (22 q  or  20 h  moves)
Martin asks:
>Is UR11 the shortest process effecting the ``odd'' element in <U,R>?

After a bit of computer cubing I found:

p183 6 Twist      R1 U3 R2 U3 R1 D3 U3 R1 U3 R3 D2 R3 U3 R1 D3 U3
                  (18 q  or  16 h  moves)

This requires using the larger group of <U1, R1, D1>, although I
expected a 16 turn process. Note the fact this larger group has face
index 3 (rather than 2). But now the process is NOT shift invariant
and we see the route itself can determine whether it will be
shift invariant!

I welcome any mathematical explanation!

With even more contemplation I noticed that the process for
the edge 3-cycle

UR1 = U3 R1 U2 (R1 U1)^2 R2 U3 R3 U3 R2 U1     (16 q, 13 h)

...was reducible to

UR1a= F1 U2 (F1 U1)^2 F2 U3 F3 U3 F2           (14 q, 11 h)]

Of course, now we are using <U1, F1> rather than <U1, R1>.

-> Mark <-
Email: mark.longridge@canrem.com

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