Bourbaki

Corollary

Tag 05PZ, permanent. Cite it as [Bourbaki, Tag 05PZ].

Algebra, chapter II, § 4. Relations between tensor products and homomorphism modules

If u1,…,upu_1, \ldots, u_p are endomorphisms of EE, then

Tr(u1∘u2∘⋯∘up)=Tr(ui∘ui+1∘⋯∘up∘u1∘⋯∘ui−1) \mathrm{Tr}(u_1 \circ u_2 \circ \cdots \circ u_p) = \mathrm{Tr}(u_i \circ u_{i+1} \circ \cdots \circ u_p \circ u_1 \circ \cdots \circ u_{i-1})

for 1≤i≤p1 \leq i \leq p ("invariance of the trace under cyclic permutation").

It suffices to apply (20) to the product

(u1∘u2∘⋯∘ui−1)∘(ui∘ui+1∘⋯∘up).(u_1 \circ u_2 \circ \cdots \circ u_{i-1}) \circ (u_i \circ u_{i+1} \circ \cdots \circ u_p).

Note that on the other hand it is not necessarily true that

Tr⁡(u∘v∘w)=Tr⁡(u∘w∘v)\operatorname{Tr}(u \circ v \circ w) = \operatorname{Tr}(u \circ w \circ v)

for three endomorphisms u,v,wu, v, w of E.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

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Cites

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Transcribed from the printed edition, 1998, Springer. Not translated.