Timeline for Normal subgroups of $SL_2$ of a polynomial ring
Current License: CC BY-SA 3.0
6 events
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| Dec 14, 2012 at 11:21 | vote | accept | Alain Valette | ||
| Dec 14, 2012 at 11:21 | comment | added | Alain Valette | Let me spell out the answer I found (thanks to Jim!) in Mason's paper quoted above (Cor. 1.4 in the paper): For $I$ an ideal in $K[X]$, generated by a polynomial of degree $\geq 2$, consider the quotient of the congruence subgroup associated to $I$, by the normal subgroup of $SL_2(K[X])$ generated by elementary matrices with coefficients in $I$: this quotient is a free non-abelian group, of finite rank if and only if $K$ is finite. This completely solves my question. | |
| Dec 6, 2012 at 16:31 | history | edited | Jim Humphreys | CC BY-SA 3.0 |
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| Dec 1, 2012 at 23:27 | history | edited | Jim Humphreys | CC BY-SA 3.0 |
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| Dec 1, 2012 at 21:52 | history | edited | Jim Humphreys | CC BY-SA 3.0 |
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| Nov 29, 2012 at 20:07 | history | answered | Jim Humphreys | CC BY-SA 3.0 |