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Obtaining signed permutation in the bruhat poset in another form

asked 2021-03-19 19:46:59 +0200

klaaa gravatar image

updated 2021-03-20 18:46:50 +0200

(I edited the question, to make it more clear)

When I input the Bruhat poset of type Bn in Sage as follows

W = WeylGroup("B2", prefix="s") 
P = W.bruhat_poset() 

the elements look like s2*s1*s2.

Question: Is there a way to represent (in the picture of the poset in Sage) the elements in the form of signed permutation as for example findstat does (see for example ) but so that - is replaced by 0 and brackets and commas are ommited? So for example all signed permutations for $n=2$ would look as follows in this notation:


(The motivation is that one can use the code in the thread to obtain the quiver algebra in GAP with names one can regognize later).

Thanks for any help

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We have

sage: W=ColoredPermutations(4,2)                                                
sage: W.category()                                                              
Category of well generated finite irreducible complex reflection groups

but this has no Bruhat order method.

FrédéricC gravatar imageFrédéricC ( 2021-03-19 20:49:19 +0200 )edit

And we have

sage: W=CoxeterGroup(['B',3])                                                   
sage: W.category()                                                              
Category of finite irreducible coxeter groups
sage: W.an_element()                                                            
[ 0  1 -a]
[ 1  1 -a]
[ 0  a -1]

which you may want to try.

FrédéricC gravatar imageFrédéricC ( 2021-03-19 20:50:47 +0200 )edit

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answered 2021-03-19 20:53:11 +0200

FrédéricC gravatar image

updated 2021-03-24 20:50:10 +0200

You can use

sage: W = WeylGroup("B2", prefix="s")                                           
sage: w=W.an_element()                                                          
sage: w.to_permutation()                                                        
(2, -1)

And relabel the poset using this map.


sage: def new_label(w): 
....:     return ''.join(str(u) for u in w.to_permutation()).replace('-','0')   
sage: W.bruhat_poset().relabel(new_label)                                       
Finite poset containing 8 elements
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Thanks, but it seems that in this form the code of the other thread can not be applied to the poset. I will do some more tests.

klaaa gravatar imageklaaa ( 2021-03-19 21:05:06 +0200 )edit

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Asked: 2021-03-19 19:46:59 +0200

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Last updated: Mar 24 '21