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Fix a second proof in algebra
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aisejohan committed May 2, 2021
1 parent c3f3232 commit c4cd811
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Expand Up @@ -179,6 +179,7 @@ John Hosack
Xiaowen Hu
Yuhao Huang
Yu-Liang Huang
Shota Inoue
Ariyan Javanpeykar
Lena Min Ji
Qingyuan Jiang
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12 changes: 6 additions & 6 deletions algebra.tex
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Expand Up @@ -1949,8 +1949,9 @@ \section{Tensor products}
Categories, Lemma \ref{categories-lemma-adjoint-exact}.

\medskip\noindent
Second direct proof. Let $P = \colim (M_i \otimes N)$, $M = \colim M_i$.
Then for all $i\leq j$, the following diagram commutes:
Second direct proof. Let $P = \colim (M_i \otimes N)$ with coprojections
$\lambda_i : M_i \otimes N \to P$. Let $M = \colim M_i$ with coprojections
$\mu_i : M_i \to M$. Then for all $i\leq j$, the following diagram commutes:
$$
\xymatrix{
M_i \otimes N \ar[r]_{\mu_i \otimes 1} \ar[d]_{\mu_{ij} \otimes 1} &
Expand All @@ -1959,10 +1960,9 @@ \section{Tensor products}
M \otimes N
}
$$
By Lemma \ref{lemma-homomorphism-limit},
these maps induce a unique homomorphism
$\psi : P \to M \otimes N$, with $\lambda_i : M_i \otimes N \to P$ given by
$\lambda_i = \pi \circ (\iota_i \otimes 1)$.
By Lemma \ref{lemma-homomorphism-limit} these maps induce a unique homomorphism
$\psi : P \to M \otimes N$ such that
$\lambda_i = \psi \circ (\mu_i \otimes 1)$.

\medskip\noindent
To construct the inverse map, for each $i\in I$, there is the canonical
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