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fix corner case of plethysm with tensors #41257

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fix corner case of plethysm with tensors #41257

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c4d48fb
fix corner case of plethysm with tensors
zabrocki Dec 3, 2025
3e35b76
point to issue in doc test
zabrocki Dec 3, 2025
23e3269
move doc test so that p and s are properly defined
zabrocki Dec 3, 2025
cdd5731
accept formatting change
zabrocki Dec 3, 2025
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9 changes: 7 additions & 2 deletions src/sage/combinat/sf/sfa.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3569,6 +3569,11 @@ def plethysm(self, x, include=None, exclude=None):
sage: (1+p[2]).plethysm(p[2])
p[] + p[4]

Fixed :issue:`41257`::

sage: s[[]](tensor([p[1], s[1]]))
p[] # s[]

Check that degree one elements are treated in the correct way::

sage: R.<a1,a2,a11,b1,b21,b111> = QQ[]
Expand Down Expand Up @@ -3646,11 +3651,11 @@ def plethysm(self, x, include=None, exclude=None):
if tensorflag:
tparents = Px._sets
lincomb = Px.linear_combination
elt = lincomb((prod(lincomb((tensor([p[r].plethysm(base(la))
elt = lincomb((prod((lincomb((tensor([p[r].plethysm(base(la))
for base, la in zip(tparents, trm)]),
_raise_variables(c, r, degree_one))
for trm, c in x)
for r in mu),
for r in mu), tensor([base.one() for base in tparents])),
d)
for mu, d in p(self))
return Px(elt)
Expand Down
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