Attempting to calculate the centralizer of a particular element of the
braid group on 5 strands causes a segmentation fault.
sage: BG = BraidGroup(5); BG
Braid group on 5 strands
sage: b = BG([3, 3, 4, 3, 3, 2, 1, 4, 3, 2]); b
s2^2*s3*s2^2*s1*s0*s3*s2*s1
sage: b.left_normal_form()
(1, s2*s3*s2, s2*s1*s0*s3*s2*s1*s0)
sage: b.ultra_summit_set()
[[s0*s1*s0*s2*s1*s0*s3*s2*s1*s0]]
sage: b.is_pseudoanosov()
False
sage: b.centralizer()
---------------------------------------------------------------------------
SignalError Traceback (most recent call last)
Cell In [7], line 1
----> 1 b.centralizer()
File /ext/sage/9.8/src/sage/groups/braid.py:1546, in Braid.centralizer(self)
1534 def centralizer(self):
1535 """
1536 Return a list of generators of the centralizer of the braid.
1537
(...)
1544
1545 """
-> 1546 l = centralizer(self)
1547 B = self.parent()
1548 return [B._element_from_libbraiding(b) for b in l]
File /ext/sage/9.8/src/sage/libs/braiding.pyx:233, in
sage.libs.braiding.centralizer()
231 return [[[0], [i+1, nstrands - i -1]] for i in
range(nstrands//2-1)] + [[[0], [nstrands//2]]]
232 l = braid.Tietze()
--> 233 sig_on()
234 cdef list[list[list[int]]] rop = CentralizerGenerators(nstrands, l)
235 sig_off()
SignalError: Segmentation fault
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