#6126: Symmetric group algebra jucys_murphy elements incorrect
---------------------------+------------------------------------------------
Reporter: arattan | Owner: mhansen
Type: defect | Status: new
Priority: minor | Milestone: sage-combinat
Component: combinatorics | Keywords: jucys_murphy
---------------------------+------------------------------------------------
The error is observed on my linux box as well as sage.math.washington.edu
(my version is 3.4.1, sage.math version is 3.4.2, the error is the same).
The error is in the function "jucys_murphy".
{{{
sage: G=SymmetricGroupAlgebra(QQ,5)
sage: PermutationOptions(mult='l2r', display='cycle')
sage: for i in range(2,6):
....: G.jucys_murphy(i)
....:
(1,2)
(2,3) + (1,2)
(3,4) + (2,3) + (1,2)
(4,5) + (3,4) + (2,3) + (1,2)
}}}
I believe the returned elements should be
{{{
(1,2)
(2,3) + (1,3)
(3,4) + (2,4) + (1,4)
(4,5) + (3,5) + (2,5) + (1,5)
}}}
I found the relevant code. On both machines the offending code is in
/usr/local/sage/devel/sage-
main/build/sage/combinat/symmetric_group_algebra.py,
and
/usr/local/sage/devel/sage-main/sage/combinat). I have fixed on my
machine by changing in those files the lines 180-185 from
{{{
------------
for i in range(1, k):
p = range(1, self.n+1)
p[i-1] = i+1
p[i] = i
res += self(p)
return res
----------------
}}}
to
{{{
------------
for i in range(1, k):
p = range(1, self.n+1)
+ p[i-1] = k
+ p[k-1] = i
res += self(p)
return res
----------------
}}}
Thanks,
Amps
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6126>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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