\documentclass[12pt,titlepage]{article} \usepackage{amsmath} \usepackage{mathrsfs} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsthm} \usepackage{mathtools} \usepackage{graphicx} \usepackage{color} \usepackage{ucs} \usepackage[utf8x]{inputenc} \usepackage{xparse} \usepackage{hyperref} %----Macros---------- % % Unresolved issues: % % \righttoleftarrow % \lefttorightarrow % % \color{} with HTML colorspec % \bgcolor % \array with options (without options, it's equivalent to the matrix environment) % Of the standard HTML named colors, white, black, red, green, blue and yellow % are predefined in the color package. Here are the rest. \definecolor{aqua}{rgb}{0, 1.0, 1.0} \definecolor{fuschia}{rgb}{1.0, 0, 1.0} \definecolor{gray}{rgb}{0.502, 0.502, 0.502} \definecolor{lime}{rgb}{0, 1.0, 0} \definecolor{maroon}{rgb}{0.502, 0, 0} \definecolor{navy}{rgb}{0, 0, 0.502} \definecolor{olive}{rgb}{0.502, 0.502, 0} \definecolor{purple}{rgb}{0.502, 0, 0.502} \definecolor{silver}{rgb}{0.753, 0.753, 0.753} \definecolor{teal}{rgb}{0, 0.502, 0.502} % Because of conflicts, \space and \mathop are converted to % \itexspace and \operatorname during preprocessing. % itex: \space{ht}{dp}{wd} % % Height and baseline depth measurements are in units of tenths of an ex while % the width is measured in tenths of an em. \makeatletter \newdimen\itex@wd% \newdimen\itex@dp% \newdimen\itex@thd% \def\itexspace#1#2#3{\itex@wd=#3em% \itex@wd=0.1\itex@wd% \itex@dp=#2ex% \itex@dp=0.1\itex@dp% \itex@thd=#1ex% \itex@thd=0.1\itex@thd% \advance\itex@thd\the\itex@dp% \makebox[\the\itex@wd]{\rule[-\the\itex@dp]{0cm}{\the\itex@thd}}} \makeatother % \tensor and \multiscript \makeatletter \newif\if@sup \newtoks\@sups \def\append@sup#1{\edef\act{\noexpand\@sups={\the\@sups #1}}\act}% \def\reset@sup{\@supfalse\@sups={}}% \def\mk@scripts#1#2{\if #2/ \if@sup ^{\the\@sups}\fi \else% \ifx #1_ \if@sup ^{\the\@sups}\reset@sup \fi {}_{#2}% \else \append@sup#2 \@suptrue \fi% \expandafter\mk@scripts\fi} \def\tensor#1#2{\reset@sup#1\mk@scripts#2_/} \def\multiscripts#1#2#3{\reset@sup{}\mk@scripts#1_/#2% \reset@sup\mk@scripts#3_/} \makeatother % \slash \makeatletter \newbox\slashbox \setbox\slashbox=\hbox{$/$} \def\itex@pslash#1{\setbox\@tempboxa=\hbox{$#1$} \@tempdima=0.5\wd\slashbox \advance\@tempdima 0.5\wd\@tempboxa \copy\slashbox \kern-\@tempdima \box\@tempboxa} \def\slash{\protect\itex@pslash} \makeatother % math-mode versions of \rlap, etc % from Alexander Perlis, "A complement to \smash, \llap, and lap" % http://math.arizona.edu/~aprl/publications/mathclap/ \def\clap#1{\hbox to 0pt{\hss#1\hss}} \def\mathllap{\mathpalette\mathllapinternal} \def\mathrlap{\mathpalette\mathrlapinternal} \def\mathclap{\mathpalette\mathclapinternal} \def\mathllapinternal#1#2{\llap{$\mathsurround=0pt#1{#2}$}} \def\mathrlapinternal#1#2{\rlap{$\mathsurround=0pt#1{#2}$}} \def\mathclapinternal#1#2{\clap{$\mathsurround=0pt#1{#2}$}} % Renames \sqrt as \oldsqrt and redefine root to result in \sqrt[#1]{#2} \let\oldroot\root \def\root#1#2{\oldroot #1 \of{#2}} \renewcommand{\sqrt}[2][]{\oldroot #1 \of{#2}} % Manually declare the txfonts symbolsC font \DeclareSymbolFont{symbolsC}{U}{txsyc}{m}{n} \SetSymbolFont{symbolsC}{bold}{U}{txsyc}{bx}{n} \DeclareFontSubstitution{U}{txsyc}{m}{n} % Manually declare the stmaryrd font \DeclareSymbolFont{stmry}{U}{stmry}{m}{n} \SetSymbolFont{stmry}{bold}{U}{stmry}{b}{n} % Manually declare the MnSymbolE font \DeclareFontFamily{OMX}{MnSymbolE}{} \DeclareSymbolFont{mnomx}{OMX}{MnSymbolE}{m}{n} \SetSymbolFont{mnomx}{bold}{OMX}{MnSymbolE}{b}{n} \DeclareFontShape{OMX}{MnSymbolE}{m}{n}{ <-6> MnSymbolE5 <6-7> MnSymbolE6 <7-8> MnSymbolE7 <8-9> MnSymbolE8 <9-10> MnSymbolE9 <10-12> MnSymbolE10 <12-> MnSymbolE12}{} % Declare specific arrows from txfonts without loading the full package \makeatletter \def\re@DeclareMathSymbol#1#2#3#4{% \let#1=\undefined \DeclareMathSymbol{#1}{#2}{#3}{#4}} \re@DeclareMathSymbol{\neArrow}{\mathrel}{symbolsC}{116} \re@DeclareMathSymbol{\neArr}{\mathrel}{symbolsC}{116} \re@DeclareMathSymbol{\seArrow}{\mathrel}{symbolsC}{117} \re@DeclareMathSymbol{\seArr}{\mathrel}{symbolsC}{117} \re@DeclareMathSymbol{\nwArrow}{\mathrel}{symbolsC}{118} \re@DeclareMathSymbol{\nwArr}{\mathrel}{symbolsC}{118} \re@DeclareMathSymbol{\swArrow}{\mathrel}{symbolsC}{119} \re@DeclareMathSymbol{\swArr}{\mathrel}{symbolsC}{119} \re@DeclareMathSymbol{\nequiv}{\mathrel}{symbolsC}{46} \re@DeclareMathSymbol{\Perp}{\mathrel}{symbolsC}{121} \re@DeclareMathSymbol{\Vbar}{\mathrel}{symbolsC}{121} \re@DeclareMathSymbol{\sslash}{\mathrel}{stmry}{12} \re@DeclareMathSymbol{\bigsqcap}{\mathop}{stmry}{"64} \re@DeclareMathSymbol{\biginterleave}{\mathop}{stmry}{"6} \re@DeclareMathSymbol{\invamp}{\mathrel}{symbolsC}{77} \re@DeclareMathSymbol{\parr}{\mathrel}{symbolsC}{77} \makeatother % \llangle, \rrangle, \lmoustache and \rmoustache from MnSymbolE \makeatletter \def\Decl@Mn@Delim#1#2#3#4{% \if\relax\noexpand#1% \let#1\undefined \fi \DeclareMathDelimiter{#1}{#2}{#3}{#4}{#3}{#4}} \def\Decl@Mn@Open#1#2#3{\Decl@Mn@Delim{#1}{\mathopen}{#2}{#3}} \def\Decl@Mn@Close#1#2#3{\Decl@Mn@Delim{#1}{\mathclose}{#2}{#3}} \Decl@Mn@Open{\llangle}{mnomx}{'164} \Decl@Mn@Close{\rrangle}{mnomx}{'171} \Decl@Mn@Open{\lmoustache}{mnomx}{'245} \Decl@Mn@Close{\rmoustache}{mnomx}{'244} \makeatother % Widecheck \makeatletter \DeclareRobustCommand\widecheck[1]{{\mathpalette\@widecheck{#1}}} \def\@widecheck#1#2{% \setbox\z@\hbox{\m@th$#1#2$}% \setbox\tw@\hbox{\m@th$#1% \widehat{% \vrule\@width\z@\@height\ht\z@ \vrule\@height\z@\@width\wd\z@}$}% \dp\tw@-\ht\z@ \@tempdima\ht\z@ \advance\@tempdima2\ht\tw@ \divide\@tempdima\thr@@ \setbox\tw@\hbox{% \raise\@tempdima\hbox{\scalebox{1}[-1]{\lower\@tempdima\box \tw@}}}% {\ooalign{\box\tw@ \cr \box\z@}}} \makeatother % \mathraisebox{voffset}[height][depth]{something} \makeatletter \NewDocumentCommand\mathraisebox{moom}{% \IfNoValueTF{#2}{\def\@temp##1##2{\raisebox{#1}{$\m@th##1##2$}}}{% \IfNoValueTF{#3}{\def\@temp##1##2{\raisebox{#1}[#2]{$\m@th##1##2$}}% }{\def\@temp##1##2{\raisebox{#1}[#2][#3]{$\m@th##1##2$}}}}% \mathpalette\@temp{#4}} \makeatletter % udots (taken from yhmath) \makeatletter \def\udots{\mathinner{\mkern2mu\raise\p@\hbox{.} \mkern2mu\raise4\p@\hbox{.}\mkern1mu \raise7\p@\vbox{\kern7\p@\hbox{.}}\mkern1mu}} \makeatother %% Fix array \newcommand{\itexarray}[1]{\begin{matrix}#1\end{matrix}} %% \itexnum is a noop \newcommand{\itexnum}[1]{#1} %% Renaming existing commands \newcommand{\underoverset}[3]{\underset{#1}{\overset{#2}{#3}}} \newcommand{\widevec}{\overrightarrow} \newcommand{\darr}{\downarrow} \newcommand{\nearr}{\nearrow} \newcommand{\nwarr}{\nwarrow} \newcommand{\searr}{\searrow} \newcommand{\swarr}{\swarrow} \newcommand{\curvearrowbotright}{\curvearrowright} \newcommand{\uparr}{\uparrow} \newcommand{\downuparrow}{\updownarrow} \newcommand{\duparr}{\updownarrow} \newcommand{\updarr}{\updownarrow} \newcommand{\gt}{>} \newcommand{\lt}{<} \newcommand{\map}{\mapsto} \newcommand{\embedsin}{\hookrightarrow} \newcommand{\Alpha}{A} \newcommand{\Beta}{B} \newcommand{\Zeta}{Z} \newcommand{\Eta}{H} \newcommand{\Iota}{I} \newcommand{\Kappa}{K} \newcommand{\Mu}{M} \newcommand{\Nu}{N} \newcommand{\Rho}{P} \newcommand{\Tau}{T} \newcommand{\Upsi}{\Upsilon} \newcommand{\omicron}{o} \newcommand{\lang}{\langle} \newcommand{\rang}{\rangle} \newcommand{\Union}{\bigcup} \newcommand{\Intersection}{\bigcap} \newcommand{\Oplus}{\bigoplus} \newcommand{\Otimes}{\bigotimes} \newcommand{\Wedge}{\bigwedge} \newcommand{\Vee}{\bigvee} \newcommand{\coproduct}{\coprod} \newcommand{\product}{\prod} \newcommand{\closure}{\overline} \newcommand{\integral}{\int} \newcommand{\doubleintegral}{\iint} \newcommand{\tripleintegral}{\iiint} \newcommand{\quadrupleintegral}{\iiiint} \newcommand{\conint}{\oint} \newcommand{\contourintegral}{\oint} \newcommand{\infinity}{\infty} \newcommand{\bottom}{\bot} \newcommand{\minusb}{\boxminus} \newcommand{\plusb}{\boxplus} \newcommand{\timesb}{\boxtimes} \newcommand{\intersection}{\cap} \newcommand{\union}{\cup} \newcommand{\Del}{\nabla} \newcommand{\odash}{\circleddash} \newcommand{\negspace}{\!} \newcommand{\widebar}{\overline} \newcommand{\textsize}{\normalsize} \renewcommand{\scriptsize}{\scriptstyle} \newcommand{\scriptscriptsize}{\scriptscriptstyle} \newcommand{\mathfr}{\mathfrak} \newcommand{\statusline}[2]{#2} \newcommand{\tooltip}[2]{#2} \newcommand{\toggle}[2]{#2} % Theorem Environments \theoremstyle{plain} \newtheorem{theorem}{Theorem} \newtheorem{lemma}{Lemma} \newtheorem{prop}{Proposition} \newtheorem{cor}{Corollary} \newtheorem*{utheorem}{Theorem} \newtheorem*{ulemma}{Lemma} \newtheorem*{uprop}{Proposition} \newtheorem*{ucor}{Corollary} \theoremstyle{definition} \newtheorem{defn}{Definition} \newtheorem{example}{Example} \newtheorem*{udefn}{Definition} \newtheorem*{uexample}{Example} \theoremstyle{remark} \newtheorem{remark}{Remark} \newtheorem{note}{Note} \newtheorem*{uremark}{Remark} \newtheorem*{unote}{Note} %------------------------------------------------------------------- \begin{document} %------------------------------------------------------------------- \section*{braided monoidal category} \hypertarget{context}{}\subsubsection*{{Context}}\label{context} \hypertarget{monoidal_categories}{}\paragraph*{{Monoidal categories}}\label{monoidal_categories} [[!include monoidal categories - contents]] \hypertarget{contents}{}\section*{{Contents}}\label{contents} \noindent\hyperlink{idea}{Idea}\dotfill \pageref*{idea} \linebreak \noindent\hyperlink{Definition}{Definition}\dotfill \pageref*{Definition} \linebreak \noindent\hyperlink{in_terms_of_higher_monoidal_structure}{In terms of higher monoidal structure}\dotfill \pageref*{in_terms_of_higher_monoidal_structure} \linebreak \noindent\hyperlink{the_2category_of_braided_monoidal_categories}{The 2-category of braided monoidal categories}\dotfill \pageref*{the_2category_of_braided_monoidal_categories} \linebreak \noindent\hyperlink{examples}{Examples}\dotfill \pageref*{examples} \linebreak \noindent\hyperlink{properties}{Properties}\dotfill \pageref*{properties} \linebreak \noindent\hyperlink{tannaka_duality}{Tannaka duality}\dotfill \pageref*{tannaka_duality} \linebreak \noindent\hyperlink{related_concepts}{Related concepts}\dotfill \pageref*{related_concepts} \linebreak \noindent\hyperlink{references}{References}\dotfill \pageref*{references} \linebreak \hypertarget{idea}{}\subsection*{{Idea}}\label{idea} Intuitively speaking, a braided monoidal category is a category with a tensor product and an isomorphism called the `braiding' which lets us `switch' two objects in a tensor product like $x \otimes y$. Thus the tensor product is ``commutative'' in a sense, but not as coherently commutative as in a [[symmetric monoidal category]]. A braided monoidal category is a special case of the notion of [[braided pseudomonoid]] in a [[braided monoidal 2-category]]. \hypertarget{Definition}{}\subsection*{{Definition}}\label{Definition} \begin{defn} \label{BraidedMonoidalCategory}\hypertarget{BraidedMonoidalCategory}{} A \textbf{braided monoidal category}, or (``braided [[tensor category]]'', but see there), is a [[monoidal category]] $\mathcal{C}$ equipped with a [[natural isomorphism]] \begin{displaymath} B_{x,y} : x \otimes y \to y \otimes x \end{displaymath} called the \textbf{[[braiding]]}, such that the following two kinds of [[commuting diagram|diagrams commute]] for all [[objects]] involved (called the \textbf{hexagon identities} encoding the compatibility of the braiding with the [[associator]] for the tensor product): \begin{displaymath} \itexarray{ (x \otimes y) \otimes z &\stackrel{a_{x,y,z}}{\to}& x \otimes (y \otimes z) &\stackrel{B_{x,y \otimes z}}{\to}& (y \otimes z) \otimes x \\ \downarrow^{B_{x,y}\otimes Id} &&&& \downarrow^{a_{y,z,x}} \\ (y \otimes x) \otimes z &\stackrel{a_{y,x,z}}{\to}& y \otimes (x \otimes z) &\stackrel{Id \otimes B_{x,z}}{\to}& y \otimes (z \otimes x) } \end{displaymath} and \begin{displaymath} \itexarray{ x \otimes (y \otimes z) &\stackrel{a^{-1}_{x,y,z}}{\to}& (x \otimes y) \otimes z &\stackrel{B_{x \otimes y, z}}{\to}& z \otimes (x \otimes y) \\ \downarrow^{Id \otimes B_{y,z}} &&&& \downarrow^{a^{-1}_{z,x,y}} \\ x \otimes (z \otimes y) &\stackrel{a^{-1}_{x,z,y}}{\to}& (x \otimes z) \otimes y &\stackrel{B_{x,z} \otimes Id}{\to}& (z \otimes x) \otimes y } \,, \end{displaymath} where $a_{x,y,z} \colon (x \otimes y) \otimes z \to x \otimes (y \otimes z)$ denotes the components of the [[associator]] of $\mathcal{C}^\otimes$. \end{defn} \begin{defn} \label{}\hypertarget{}{} If the braiding in def. \ref{BraidedMonoidalCategory} ``squares'' to the identity in that $B_{y,x} \circ B_{x,y} = id_{x \otimes y}$, then the braided monoidal category is called a \emph{[[symmetric monoidal category]]}. \end{defn} \begin{remark} \label{}\hypertarget{}{} Intuitively speaking, the first hexagon identity in def. \ref{BraidedMonoidalCategory} says we may braid $x$ past $y \otimes z$ `all at once' or in two steps. The second hexagon identity says that we may braid $x \otimes y$ past $z$ all at once or in two steps. \end{remark} \begin{remark} \label{}\hypertarget{}{} From these axioms in def. \ref{BraidedMonoidalCategory}, it follows that the braiding is compatible with the left and right [[unitors]] $l_x : I \otimes x \to x$ and $r_x : x \otimes I \to x$. That is to say, for all objects $x$ the diagram \begin{displaymath} \itexarray{ I \otimes x &&\stackrel{B_{I,x}}{\to}&& x \otimes I \\ & {}_{l_x}\searrow && \swarrow_{r_x} \\ && x } \end{displaymath} commutes. \end{remark} \hypertarget{in_terms_of_higher_monoidal_structure}{}\subsubsection*{{In terms of higher monoidal structure}}\label{in_terms_of_higher_monoidal_structure} In terms of the language of [[k-tuply monoidal n-categories]] a braided monoidal category is a \emph{doubly monoidal 1-category} . Accordingly, by [[delooping]] twice, it may be identified with a [[tricategory]] with a single [[object]] and a single 1-[[morphism]]. However, unlike the definition of a monoidal category as a [[bicategory]] with one object, this identification is not trivial; a doubly-degenerate tricategory is literally a category with two monoidal structures that [[interchange law|interchange]] up to isomorphism. It requires the [[Eckmann-Hilton argument]] to deduce an equivalence with braided monoidal categories. A commutative [[monoid]] is the same as a monoid [[internalization|in the category of]] monoids. Similarly, a braided monoidal category is equivalent to a monoidal-category object (that is, a [[pseudomonoid]]) in the monoidal 2-category of monoidal categories. This result goes back to the \href{http://maths.mq.edu.au/~street/JS1.pdf}{1986 paper by Joyal and Street}. (There is also a notion of [[braided pseudomonoid]] that specializes directly in [[Cat]] to braided monoidal categories.) A braided monoidal category is equivalently a category that is equipped with the structure of an [[algebra over an operad|algebra over]] the [[little cubes operad|little 2-cubes operad]]. Details are in example 1.2.4 of \begin{itemize}% \item [[Jacob Lurie]], $\mathbb{E}[k]$-[[Ek-Algebras|Algebras]] \end{itemize} \hypertarget{the_2category_of_braided_monoidal_categories}{}\subsubsection*{{The 2-category of braided monoidal categories}}\label{the_2category_of_braided_monoidal_categories} There is a [[strict 2-category]] BrMonCat with: \begin{itemize}% \item braided monoidal categories as objects, \item [[braided monoidal functor|braided monoidal functors]] as morphisms, \item [[braided monoidal natural transformation|braided monoidal natural transformations]] as 2-morphisms. \end{itemize} \hypertarget{examples}{}\subsection*{{Examples}}\label{examples} \begin{itemize}% \item Any [[symmetric monoidal category]] is a braided monoidal category. \item The monoidal category $R$-$\mathcal{GMod}$ of [[graded modules]] over a [[commutative ring]] $R$ (with the usual [[tensor product of modules|tensor product of graded modules]]) can be made into a braided monoidal category in multiple ways, each one given by an invertible element $u$ of the base ring. Infact, all braidings on $R$-$\mathcal{GMod}$ arise in this way (as in \href{JoyalStreet86}{Joyal, Street}). The braiding $B^u_{V,W} : V \otimes W \to W \otimes V$, is defined as \begin{displaymath} x \otimes y \mapsto u^{|x||y|} y \otimes x, \end{displaymath} where $|x|$ and $|y|$ denote the degrees. It's evident that the resulting braided monoidal category is symmetric if and only if $u^2 = 1$. \item The category of [[crossed G-set|crossed G-sets]]. \end{itemize} \hypertarget{properties}{}\subsection*{{Properties}}\label{properties} \hypertarget{tannaka_duality}{}\subsubsection*{{Tannaka duality}}\label{tannaka_duality} [[!include structure on algebras and their module categories - table]] \hypertarget{related_concepts}{}\subsection*{{Related concepts}}\label{related_concepts} \begin{itemize}% \item [[k-tuply monoidal (n,r)-category]] \item [[monoidal category]], [[monoidal (∞,1)-category]] \item \textbf{braided monoidal category}, [[braided monoidal (∞,1)-category]] \begin{itemize}% \item [[braided 2-group]], [[braided ∞-group]] \item [[braided monoidal 2-category]] \end{itemize} \item [[symmetric monoidal category]], [[symmetric monoidal (∞,1)-category]] \item [[closed monoidal category]] , [[closed monoidal (∞,1)-category]] \item [[2-fold monoidal category]], [[duoidal category]] \end{itemize} \hypertarget{references}{}\subsection*{{References}}\label{references} Exposition of basics of [[monoidal categories]] and [[categorical algebra]]: \begin{itemize}% \item \emph{[[geometry of physics -- categories and toposes]]}, Section 2: \emph{\href{geometry+of+physics+--+categories+and+toposes#BasicNotionsOfCategoricalAlgebra}{Basic notions of categorical algebra}} \end{itemize} The original papers on braided monoidal categories are by [[Andre Joyal|Joyal]] and [[Ross Street|Street]]. The published version does not completely supersede the \emph{Macquarie Math Reports} version, which has some nice extra results: \begin{itemize}% \item [[André Joyal]] and [[Ross Street]], \href{http://maths.mq.edu.au/~street/JS1.pdf}{Braided monoidal categories}, \emph{Macquarie Math Reports} \textbf{860081} (1986). \item [[André Joyal]] and [[Ross Street]], \emph{Braided tensor categories} , Adv. Math. \textbf{102} (1993), 20--78. \end{itemize} Around the same time the same definition was also proposed independently by [[Lawrence Breen]] in a letter to [[Pierre Deligne]]: \begin{itemize}% \item [[Lawrence Breen]], \emph{Une lettre \`a{} P. Deligne au sujet des $2$-cat\'e{}gories tress\'e{}es} (1988) (\href{http://www.math.univ-paris13.fr/~breen/deligne.pdf}{pdf}) \end{itemize} Textbook accounts include \begin{itemize}% \item [[nLab:Pavel Etingof]], Shlomo Gelaki, Dmitri Nikshych, [[nLab:Victor Ostrik]], chapter 2 of \emph{Tensor categories}, Mathematical Surveys and Monographs, Volume 205, American Mathematical Society, 2015 (\href{http://www-math.mit.edu/~etingof/egnobookfinal.pdf }{pdf}) \end{itemize} For a review of definitions of braided monoidal categories, braided monoidal functors and braided monoidal natural transformations, see: \begin{itemize}% \item [[John Baez]], \href{http://math.ucr.edu/home/baez/qg-fall2004/definitions.pdf}{Some definitions everyone should know}. \end{itemize} For an elementary introduction to braided monoidal categories using [[string diagram]]s, see: \begin{itemize}% \item [[John Baez]] and [[Mike Stay]], \href{http://math.ucr.edu/home/baez/rosetta.pdf}{Physics, topology, logic and computation: a Rosetta Stone}, to appear in \emph{New Structures in Physics}, ed. Bob Coecke. \end{itemize} Eventually we should include all these diagrams here, along with the definition of braided monoidal functor and braided monoidal natural transformation! Can anyone help out? [[!redirects braided monoidal category]] [[!redirects braided monoidal categories]] [[!redirects braided category]] [[!redirects braided categories]] [[!redirects braided tensor category]] [[!redirects braided tensor categories]] [[!redirects hexagon identity]] [[!redirects hexagon identities]] \end{document}