|
Theorem. Bédard's figure is generated by a finite automaton.
Proof :
-
The language of reduced words (as well as that of ShortLex words) for a Coxeter group is
regular (Brink & Howlett).
ShortLex tree for affine A2
and its minimal version
-
The set of words containing one side of a braid relation
(a braid word) is regular.
-
The set of reduced words with a unique reduced expression is that
of reduced words containing no braid words (Tits).
-
[ unique reduced words ]
= [ reduced words ] AND NOT [ containing braid word ]
|
