From 356ac56be0a79b9d10f3f4fcf4f3666c7194c7bc Mon Sep 17 00:00:00 2001
From: jgarnek <jgarnek@amu.edu.pl>
Date: Mon, 2 Dec 2024 21:01:06 +0100
Subject: [PATCH] etale case new pt 1

---
 article_de_rham_cyclic.tex | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/article_de_rham_cyclic.tex b/article_de_rham_cyclic.tex
index c979f5d..16c188f 100644
--- a/article_de_rham_cyclic.tex
+++ b/article_de_rham_cyclic.tex
@@ -667,9 +667,20 @@ Let $X$ be a curve with an action of $G$ and write $Y := X/H$. For any $k[C]$-mo
 \end{proof}
 
 \begin{proof}[Proof of Main Theorem]
-	As explained at the beginning of this section, it suffices to show this in the case when $G = H \rtimes_{\chi} C = \langle \sigma \rangle \rtimes_{\chi} \langle \rho \rangle \cong \ZZ/p^n \rtimes_{\chi} \ZZ/c$ and $k  \ol k$ by Lemma~\ref{lem:reductions}.
+	As explained at the beginning of this section, it suffices to show this in the case when $G = H \rtimes_{\chi} C = \langle \sigma \rangle \rtimes_{\chi} \langle \rho \rangle \cong \ZZ/p^n \rtimes_{\chi} \ZZ/c$ and $k = \ol k$ by Lemma~\ref{lem:reductions}.
 	We prove this by induction on $n$. If $n = 0$, then it follows by Chevalley--Weil theorem.
 	Consider now two cases. Firstly, we assume that $X \to Y$ is \'{e}tale.
+	Note that the proof of Lemma~\ref{lem:G_invariants_\'{e}tale} implies
+	that there exists an exact sequence:
+	%
+	\[
+		0 \to k \to H^1_{dR}(Y) \to T^1 \mc M \to k \to 0.
+	\]
+	%
+	Therefore, since the category of $k[C]$-modules is semisimple, $T^1 \mc M \cong H^1_{dR}(Y)$. By induction hypothesis we conclude that
+	$T^1 \mc M$ is determined by higher ramification data.
+	
+	
 	Recall that by proof of Theorem~\ref{thm:cyclic_de_rham}, the map $(\sigma - 1)$
 	is an isomorphism of $k$-vector spaces between $T^{i+1} \mc M$ and $T^i \mc M$ for
 	$i = 2, \ldots, p^n$. This yields an isomorphism of $k[C]$-modules for $i \ge 2$ by Lemma~\ref{lem:TiM_isomorphism_hypoelementary}: