Bourbaki

Remark 3

Tag 0DVN, permanent. Cite it as [Bourbaki, Tag 0DVN].

Algebra, chapter X, § 4. Produits de torsion

If g:N→N′g : N \to N' is a homomorphism of left A-modules, then

(1L(M)⊗g)∘(1L(M)⊗1N)=(1L(M)⊗1N)∘(1L(M)⊗L(g)), (1_{L(M)} \otimes g) \circ (1_{L(M)} \otimes 1_N) = (1_{L(M)} \otimes 1_N) \circ (1_{L(M)} \otimes L(g)) ,

therefore the diagram

TorA(M,N)→ψM(N)H(L(M)⊗AN)TorA(1,g)↓↓H(1⊗g)TorA(M,N′)→ψM(N′)H(L(M)⊗AN′) \begin{array}{ccc} \mathrm{Tor}^A(M, N) & \xrightarrow{\psi_{M(N)}} & H(L(M) \otimes_A N) \\ \mathrm{Tor}^A(1, g) \downarrow & & \downarrow H(1 \otimes g) \\ \mathrm{Tor}^A(M, N') & \xrightarrow{\psi_{M(N')}} & H(L(M) \otimes_A N') \end{array}

is commutative.

Analogously, if f:M→M′f : M \to M' is a homomorphism of right A-modules, one has a commutative diagram :

TorA(M,N)→ψ‾N(M)H(M⊗AL(N))TorA(f,1)↓↓H(f⊗1)TorA(M′,N)→ψ‾N(M′)H(M′⊗AL(N)). \begin{array}{ccc} \mathrm{Tor}^A(M, N) & \xrightarrow{\overline{\psi}_{N(M)}} & H(M \otimes_A L(N)) \\ \mathrm{Tor}^A(f, 1) \downarrow & & \downarrow H(f \otimes 1) \\ \mathrm{Tor}^A(M', N) & \xrightarrow{\overline{\psi}_{N(M')}} & H(M' \otimes_A L(N)) . \end{array}

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

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Cites

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