我怎样才能在&还有这两条线？
致谢米科感谢令人惊叹的 MWE。
\documentclass{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=1in]{geometry}
\usepackage[english,spanish,french]{babel}
\addto\captionsspanish{\renewcommand{\listtablename}{Índice de tablas}}
\usepackage{tocloft}
\renewcommand{\cftchapfont}{\normalfont}
\usepackage{lipsum} % filler text
\usepackage{fancyhdr}
\usepackage[Sonny]{fncychap}
%\usepackage{titlesec}
%%\titleformat*{\part}{\LARGE\bfseries}
%\titleformat*{\section}{\LARGE\bfseries}
%\titleformat*{\subsection}{\Large\bfseries}
%\titleformat*{\subsubsection}{\large\bfseries}
%\titleformat*{\paragraph}{\large\bfseries}
%\titleformat*{\subparagraph}{\large\bfseries}
\usepackage{sectsty}
\partfont{\Huge}
\chapterfont{\huge}
\sectionfont{\LARGE}
\subsectionfont{\Large}
\subsubsectionfont{\large}
\paragraphfont{\large}
\subparagraphfont{\large}
%% load the hyperref package last:
\usepackage[colorlinks,allcolors=blue]{hyperref}
\begin{document}
\tableofcontents
\part{Theoretical background \\ \& \\ state of the art}
\chapter*{Introduction}
\chapter{Détection de véhicules: \'Etat de l'art}
\section{Test section}
\subsection{Test subsection}
\subsubsection{Test subsubsection}
\paragraph{Test paragraph}
\lipsum[2]
\subparagraph{Test subparagraph}
\lipsum[2]
\end{document}