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Re: Symmetrizing function arguments

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  • Subject: [mg127617] Re: Symmetrizing function arguments
  • From: Hauke Reddmann <fc3a501 at>
  • Date: Wed, 8 Aug 2012 21:31:59 -0400 (EDT)
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  • References: <jvqem1$gtt$> <jvt3oc$lum$>

Nasser M. Abbasi <nma at> wrote:
> On 8/7/2012 2:04 AM, Hauke Reddmann wrote:

>> 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]];

> why not simply use Sort, that is what you are doing above?

a) because I am a n00b :-), but more relevant b):
these were examples, but the actual 6j symbols are NOT
invariant under Sort, just under tetrahedral symmetry!
I.e. 6j[a,b,c,d,e,f]=6j[c,d,a,b,e,f] (and likewise for the
third pair e,f) and 6j[a,b,c,d,e,f]=6j[a,b,d,c,f,e]
(and likewise all other double swaps). So applying Sort
correctly is not that trivial. 

Hauke Reddmann <:-EX8    fc3a501 at
Out on deck the dawn arrived
Your grey sweater oversized
The rooftops glimmered before our eyes

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