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Let $F =$ the free group generated by $\Sigma \cup V$ where $\Sigma = \Sigma(s)$ is the minimal alphabet that $s$ is over, and $V = \{V_1, \dots, V_n\}$ is a finite set of variables.
I would like to quotient by the smallest normal subgroup containing all of $V_i^{-1} v_i$ where $v_i = $ a substr...
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Here is another solution using only the Cayley-Hamilton Theorem for finitely generated modules (Proposition 2.4. in Atiyah-Macdonald) which, even though looks quite innocent, is a very powerful statement.
Assume by contradiction that there is an injective map $\phi: A^m \to A^n$ with $m>n$. The ...
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