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get ch3 LaTeX compiling
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blueprint/src/chapter/ch03frey.tex

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@@ -174,14 +174,14 @@ \section{Multiplicative reduction}
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and with perfect residue field, and if $E$ has multiplicative reduction, then there's
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an unramified character $\chi$ of $\Gal(K^{\sep}/K)$ whose square is 1, such that for
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all positive integers $n$ with $n\not=0$ in $K$, the
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$n$-torsion $E(K^{\sep})[n]$ is an extension of $\chi$ by $\eps\chi$, where $\eps$ is the
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$n$-torsion $E(K^{\sep})[n]$ is an extension of $\chi$ by $\epsilon\chi$, where $\epsilon$ is the
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cyclotomic character.
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\end{corollary}
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\begin{proof} After a quadratic twist we may assume that $E$ has split multiplicative reduction.
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The result then follows from the uniformisation theorem and an explicit computation.
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Note that even if we do not prove surjectivity of Tate's uniformisation, we still know
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that it's surjective on the $n$-torsion, because all $n^2$ point in the $n$-torsion of $E$
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are accounted for by the $n$-torsion in $K^{\sep}^\times/q^{\mathbb{Z}}$.
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are accounted for by the $n$-torsion in $(K^{\sep})^\times/q^{\mathbb{Z}}$.
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\end{proof}
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\section{Hardly ramified representations}
@@ -208,15 +208,16 @@ \section{Hardly ramified representations}
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devoted to a proof of this. The proof is standard; for another reference, see Theorem~2.15
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of~\cite{ddt}.
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\section{The $\ell$-torsion in the Frey curve is hardly ramified.}
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\section{The l-torsion in the Frey curve is hardly ramified.}
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Let $(a,b,c,\ell)$ be a Frey package, with associated Frey curve $E$ and mod $\ell$ Galois
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representation $\rho=E[\ell]$. We now work through a proof that $\rho$ is hardly ramified.
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\begin{theorem}\label{Frey_curve_good} If $p\not=\ell$ is a prime not dividing $abc$ then
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$\rho$ is unramified at~$p$.
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\end{theorem}
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\begin{proof} Indeed, $E$ has good reduction at $p$, and hence $\rho$ is unramified at $p$ by~ref{good_reduction_implies_unramified}.
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\begin{proof} Indeed, $E$ has good reduction at $p$, and hence $\rho$ is unramified at $p$
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by~\ref{good_reduction_implies_unramified}.
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\end{proof}
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If however $p$ divides $abc$ then $E$ has multiplicative
@@ -265,8 +266,12 @@ \section{The $\ell$-torsion in the Frey curve is hardly ramified.}
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\begin{theorem}\label{Frey_curve_mod_ell_rep_at_ell} Let $\rho$ be the $\ell$-torsion in the
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Frey curve associated to a Frey package $(a,b,c,\ell)$. Then the restriction of $\rho$ to $\GQl$ comes from a finite flat group scheme.
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\end{theorem}
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\begin{proof} The Frey curve either has good reduction at $\ell$ (case 1 of FLT) or multiplicative reduction at $\ell$ (case 2 of FLT). In the first case the $\ell$-torsion is finite and flat
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at $\ell$ by theorem~ref{good_reduction_implies_flat}. In the second case the theory of the Tate curve shows that the $\ell$-torsion is (up to quadratic twist) an \emph{unramified} extension of the trivial character by the cyclotomic character, and furthermore that the extension is controlled
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\begin{proof} The Frey curve either has good reduction at $\ell$ (case 1 of FLT) or multiplicative
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reduction at $\ell$ (case 2 of FLT). In the first case the $\ell$-torsion is finite and flat
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at $\ell$ by theorem~\ref{good_reduction_implies_flat}. In the second case the theory of the Tate
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curve shows that the $\ell$-torsion is (up to quadratic twist) an \emph{unramified} extension of
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the trivial character by the cyclotomic character, and furthermore that the extension is
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controlled
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by the $\ell$th power of an $\ell$-adic unit. This extension is known to be finite and flat;
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see for example Proposition~8.2 of~\cite{edix}.
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\end{proof}
@@ -284,7 +289,7 @@ \section{The $\ell$-torsion in the Frey curve is hardly ramified.}
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theorem~\ref{frey_curve_at_2}, and the fourth is theorem~\ref{Frey_curve_mod_ell_rep_at_ell}.
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\end{proof}
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\section{The $\ell$-torsion in the Frey curve is irreducible.}
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\section{The l-torsion in the Frey curve is irreducible.}
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We finish this chapter by showing that Mazur's theorem implies that the $\ell$-torsion in the Frey
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curve is irreducible.

blueprint/src/macro/common.tex

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\newcommand{\Z}{\mathbb{Z}}
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\newcommand{\Q}{\mathbb{Q}}
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\newcommand{\Qp}{\mathbb{Q}_p}
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\newcommand{\Ql}{\mathbb{Q}_\ell}
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\newcommand{\Qbar}{\overline{\Q}}
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\newcommand{\Qpbar}{\overline{\Q}_p}
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\newcommand{\Qlbar}{\overline{\Q}_\ell}
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\newcommand{\bbC}{\mathbb{C}}
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\newcommand{\GQ}{\Gal(\Qbar/\Q)}
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\newcommand{\GQp}{\Gal(\Qpbar/\Qp)}
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\newcommand{\GQl}{\Gal(\Qlbar/\Ql)}
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\newcommand{\m}{\mathfrak{m}}
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\DeclareMathOperator{\Gal}{Gal}
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\DeclareMathOperator{\Aut}{Aut}

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