Symmetrizing function arguments
- To: mathgroup at smc.vnet.net
- Subject: [mg127608] Symmetrizing function arguments
- From: Hauke Reddmann <fc3a501 at uni-hamburg.de>
- Date: Tue, 7 Aug 2012 03:01:26 -0400 (EDT)
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I'd like to define a quasi 6j symbol which has tetrahedron symmetry in its 6 arguments. At the moment (I'm a n00b, still :-) I use a cheap hack: f[a_,b_] := If[a>b,F[a,b],F[b,a]]; Bingo, f now is commutative and sorts by descending arguments, and NOOOOO endless loops. My, am I proud of myself :-) Needless to say, using this method to implement the symmetries of h[a_,b_,c_,d_,e_,f] is a royal pain in the backside, as you see with the hassle needed already for just 3 arguments... g[a_,b_,c_]:=If[b>c,If[a>c,If[a>b,G[a,b,c],g[b,a,c]],g[c,b,a]],g[a,c,b]]; ...especially considering all the subcases needed when two arguments are equal. Surely, you can offer a more elegant way? It more or less suffices to bring the largest value to position 1 and the second-largest to 2 or 3 (assume a,b and c,d and e,f are the opponent edges of the tetrahedron), but optimal would be if none of the 24 tetrahedron operations gives a smaller lexicalic ordering even in the case of equal entries. P.S. No, the inbuilt 6j symbol is useless - wrong Lie group :-) -- Hauke Reddmann <:-EX8 fc3a501 at uni-hamburg.de Out on deck the dawn arrived Your grey sweater oversized The rooftops glimmered before our eyes
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