From 0089fd1369af66dd7f694d18290f4f677b5046ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20M=C3=BCller?= <andreas.mueller@ost.ch>
Date: Thu, 13 May 2021 18:05:26 +0200
Subject: add new slides

---
 vorlesungen/slides/8/chrwilf.tex | 115 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 vorlesungen/slides/8/chrwilf.tex

(limited to 'vorlesungen/slides/8/chrwilf.tex')

diff --git a/vorlesungen/slides/8/chrwilf.tex b/vorlesungen/slides/8/chrwilf.tex
new file mode 100644
index 0000000..7edb10e
--- /dev/null
+++ b/vorlesungen/slides/8/chrwilf.tex
@@ -0,0 +1,115 @@
+%
+% chrwilf.tex -- slide template
+%
+% (c) 2021 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
+%
+\bgroup
+\setlength{\abovedisplayskip}{5pt}
+\setlength{\belowdisplayskip}{5pt}
+\def\kante#1#2{
+	\draw[shorten >= 0.2cm,shorten <= 0.2cm] (#1) -- (#2);
+}
+\def\knoten#1#2{
+	\uncover<8->{
+		\fill[color=#2!30] (#1) circle[radius=0.2];
+		\draw[color=#2] (#1) circle[radius=0.2];
+	}
+	\only<-7>{
+		\draw (#1) circle[radius=0.2];
+	}
+}
+\def\R{1.5}
+\definecolor{rot}{rgb}{1,0,0}
+\definecolor{gruen}{rgb}{0,0.6,0}
+\definecolor{blau}{rgb}{0,0,1}
+\begin{frame}[t]
+\frametitle{Schranke für die chromatische Zahl}
+\vspace{-20pt}
+\begin{columns}[t,onlytextwidth]
+\begin{column}{0.48\textwidth}
+\begin{block}{Satz (Wilf)}
+$\uncover<2->{\operatorname{chr}(X) \le 1+}\alpha_{\text{max}} \le\uncover<2->{ 1 + }d$
+\end{block}
+\uncover<3->{%
+\begin{block}{Beispiel}
+\begin{align*}
+\uncover<4->{d&= 4}
+&&\uncover<5->{\Rightarrow& \operatorname{chr}(G) &\le 5}\\
+\uncover<6->{\alpha_{\text{max}} &= 
+2.9565}
+&&\uncover<7->{\Rightarrow& \operatorname{chr}(G) &\le 3}\\
+\uncover<4->{\overline{d} &= \frac{24}{9}=\rlap{$2.6666$}}
+\end{align*}
+\vspace{-20pt}
+\begin{center}
+\begin{tikzpicture}[>=latex,thick]
+
+\coordinate (A) at (0:\R);
+\coordinate (B) at (40:\R);
+\coordinate (C) at (80:\R);
+\coordinate (D) at (120:\R);
+\coordinate (E) at (160:\R);
+\coordinate (F) at (200:\R);
+\coordinate (G) at (240:\R);
+\coordinate (H) at (280:\R);
+\coordinate (I) at (320:\R);
+
+\knoten{A}{rot}
+\knoten{B}{blau}
+\knoten{C}{gruen}
+\knoten{D}{blau}
+\knoten{E}{rot}
+\knoten{F}{blau}
+\knoten{G}{rot}
+\knoten{H}{gruen}
+\knoten{I}{blau}
+
+\kante{A}{B}
+\kante{B}{C}
+\kante{C}{D}
+\kante{D}{E}
+\kante{E}{F}
+\kante{F}{G}
+\kante{G}{H}
+\kante{H}{I}
+\kante{I}{A}
+
+\kante{A}{C}
+\kante{A}{D}
+\kante{D}{G}
+
+\end{tikzpicture}
+\end{center}
+\end{block}}
+\end{column}
+\begin{column}{0.52\textwidth}
+\uncover<9->{%
+\begin{proof}[Beweis]
+Induktion nach der Grösse $n$ des Graphen.
+\begin{itemize}
+\item<10->
+Entferne $v\in X$ mit minimalem Grad: $X'=X\setminus \{v\}$
+\item<11->
+Induktionsannahme:
+\[
+\operatorname{chr}(X')
+\le
+1+
+\alpha_{\text{max}}' 
+\]
+\item<12->
+$X'$ kann mit höhcstens $1+\alpha_{\text{max}}'\le 1+\alpha_{\text{max}}$
+Farben eingefärbt werden.
+\item<13->
+Wegen
+\(
+\deg(v) \le \overline{d} \le \alpha_{\text{max}}
+\)
+hat $v$ höchstens $\alpha_{\text{max}}$ Nachbarn, um $v$ zu färben,
+braucht man also höchstens $1+\alpha_{\text{max}}$ Farben.
+\end{itemize}
+\end{proof}}
+\end{column}
+\end{columns}
+\end{frame}
+\egroup
-- 
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