\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*{geometric function object} \hypertarget{content}{}\section*{{Content}}\label{content} \noindent\hyperlink{content}{Content}\dotfill \pageref*{content} \linebreak \noindent\hyperlink{idea}{Idea}\dotfill \pageref*{idea} \linebreak \noindent\hyperlink{overcategories_and_groupoidification}{over-categories and groupoidification}\dotfill \pageref*{overcategories_and_groupoidification} \linebreak \noindent\hyperlink{remarks}{remarks}\dotfill \pageref*{remarks} \linebreak \noindent\hyperlink{undercategories_of_quantities}{under-categories of $\infty$-quantities}\dotfill \pageref*{undercategories_of_quantities} \linebreak \noindent\hyperlink{quasicoherent_sheaves}{quasicoherent sheaves}\dotfill \pageref*{quasicoherent_sheaves} \linebreak \hypertarget{idea}{}\section*{{Idea}}\label{idea} This entry list details on concrete constructions for examples of [[geometric function theory|geometric function theories]], or closely related structures. Recall the notion of \emph{geometric function object} from [[geometric function theory]]: Given an [[(∞,1)-topos]] $\mathbf{H}$ of [[∞-stack]]s -- in the simplest case just [[Top]] or [[∞-Grpd]] -- a \emph{geometric function theory} is some kind of assignment \begin{displaymath} C : \mathbf{H} \to (\infty,1)Cat \end{displaymath} such that for $X \in \mathbf{H}$ the object $C(X)$ behaves to some useful extent like a collection of ``functions on $X$''. More concretely, this will usually be taken to mean that $C$ satisfies properties of the following kind: \begin{itemize}% \item \textbf{existence of pull-push} -- For every morphism $f : A \to B$ in $\mathbf{H}$ there is naturally (functorially) an [[adjunction]] $f_* : C(A) \stackrel{\leftarrow}{\to} C(B) : f^*$ with $f_*$ playing the role of push-forward of functions along $f$ and $f^*$ playing the role of pullback of functions along $f$; \item \textbf{respect for composition of spans} -- Pull-push through [[span]]s should be functorial: if \begin{displaymath} \itexarray{ &&&& Y_1 \times_{X_2} Y_2 \\ &&& {}^{p_1}\swarrow && \searrow^{p_2} \\ && Y_1 &&&& Y_2 \\ & {}^t\swarrow && \searrow^u && {}^v\swarrow && \searrow^w \\ X_1 &&&& X_2 &&&& X_4 } \end{displaymath} is a composite of two [[span]]s, then the pull-push through both spans seperately should be equivalent to that through the total span \begin{displaymath} w_* v^* u_* t^* \simeq {w}_* {p_2}_* p_1^* t^* \,. \end{displaymath} Of course this just means that the two ways to pull-push through the pullback diamond \begin{displaymath} \itexarray{ &&&& Y_1 \times_{X_2} Y_2 \\ &&& {}^{p_1}\swarrow && \searrow^{p_2} \\ && Y_1 &&&& Y_2 \\ & && \searrow^u && {}^v\swarrow && \\ &&&& X_2 &&&& } \end{displaymath} should coincide. \item \textbf{respect for fiber products} -- With respect to some suitable [[tensor product]] of geometric functions one has for each ([[homotopy pullback|homotopy]]) [[fiber product]] $X \times_Z Y$ in $\mathbf{H}$ that \begin{displaymath} C(X \times_Z Y) \simeq C(X) \otimes_{C(Z)} C(Y) \,. \end{displaymath} \end{itemize} \hypertarget{overcategories_and_groupoidification}{}\subsection*{{over-categories and groupoidification}}\label{overcategories_and_groupoidification} This first example is rather minimalistic and may feel a bit tautological, as compared to more involved constructions as discussed below. It does nevertheless have interesting applications and, due to its structural simplicity, should serve as a good model on which to study the structural aspects of geometric function theory. So consider here the assignment \begin{displaymath} C := \mathbf{H}/(-) : \mathbf{H} \to (\infty,1)Cat \end{displaymath} that sends each object $X \in \mathbf{H}$ to its [[over category]] $\mathbf{H}/X$. Checking that this assignment does satisfy a good deal of the properties of a geometric function object amounts to recalling the properties of [[over category|over categories]]. So an [[object]] in $C(X)$ is a morphism $\psi : \Psi \to X$ in $\mathbf{H}$. A [[morphism]] $(\psi,\Psi) \to (\psi',\Psi')$ is a diagram \begin{displaymath} \itexarray{ \Psi &&\to&& \Psi' \\ & {}_\psi\searrow && \swarrow_{\psi'} \\ && X } \end{displaymath} in $\mathbf{H}$. For $f : X \to Y$ a morphism in $\mathbf{H}$ the push-forward functor \begin{displaymath} f_* : C(X) \to C(Y) \end{displaymath} is simply given by postcomposition with $f$: \begin{displaymath} f_* \;\;:\;\; \left( \itexarray{ \Psi \\ \downarrow^\psi \\ X } \right) \;\; \mapsto \;\; \left( \itexarray{ \Psi \\ \downarrow^\psi \\ X \\ \downarrow^f \\ Y } \right) \,. \end{displaymath} The pullback functor \begin{displaymath} f^* : C(Y) \to C(X) \end{displaymath} is literally given by the ([[homotopy pullback|homotopy]]) [[pullback]] \begin{displaymath} \itexarray{ f^* \Psi &\to& \Psi \\ \downarrow^{f^* \psi} && \downarrow^\psi \\ X &\stackrel{f}{\to}& Y } \end{displaymath} of a morphism $\psi : \Psi \to Y$ along $f$. A quick way to check that pushforward $f_*$ and pullback $f^*$ defined this form a pair of [[adjoint functor]]s is to notice the hom-isomorphism \begin{displaymath} Hom_{\mathbf{H}/X}(\Psi, f^* \Phi) \simeq Hom_{\mathbf{H}/X}(f_* \Psi, \Phi) \end{displaymath} which is established by the essential uniqueness of the universal morphism into the pullback \begin{displaymath} \itexarray{ \Psi &&\to&& \\ & \searrow^{\exists ! \bar k} & && \downarrow^{k} \\ \downarrow && f^* \Phi &\to& \Phi \\ &\searrow& \downarrow^{f^* \psi} && \downarrow^\psi \\ && X &\stackrel{f}{\to}& Y } \end{displaymath} Here the outer diagram exhibits a morphism $k : f_* \Psi \to \Phi$. The universal property of the [[pullback]] says that this essentially uniquely corresponds to the [[adjunct]] morphism $\bar k : \Psi \to f^* \Phi$. The fact that the pull-push respects composition of spans is a direct consequence of the way [[pullback]] diagrams compose under pasting: recall that in a diagram \begin{displaymath} \itexarray{ A &\to& B &\to& C \\ \downarrow && \downarrow && \downarrow \\ D &\to& E &\to& F } \end{displaymath} for which the left square is a pullback, the total rectangle is a pullback precisely if the right square is, too. Apply this to the pull-push of an object $\left(\itexarray{ \Psi \\ \downarrow^{\psi} \\ Y_1}\right) \in C(Y_1)$ through a pullback diamond (see the introduction above) \begin{displaymath} \itexarray{ &&&& Y_1 \times_{X_2} Y_2 \\ &&& {}^{p_1}\swarrow && \searrow^{p_2} \\ && Y_1 &&&& Y_2 \\ & && \searrow^u && {}^v\swarrow && \\ &&&& X_2 &&&& } \,. \end{displaymath} This is described by the diagram \begin{displaymath} \itexarray{ && p_1^* \Psi \\ & {}^{q_1}\swarrow && \searrow^{p_1^* \psi} \\ \Psi&&&& Y_1 \times_{X_2} Y_2 \\ &\searrow^f && {}^{p_1}\swarrow && \searrow^{p_2} \\ && Y_1 &&&& Y_2 \\ & && \searrow^u && {}^v\swarrow && \\ &&&& X_2 &&&& } \,. \end{displaymath} By the above definitions, the push-pull operation $v^* u_*$ is encoded in the pullback property of the total outer rectangle. On the other hand, the pull-push operation ${p_2}_* p_1^*$ is determined by the pullback property of the upper square. By the above fact both properties are equivalent. This means that indeed \begin{displaymath} v^* u_* \simeq {p_2}_* p_1^* \end{displaymath} and hence that the pull-push operations defined by over-categories are compatible with composition of [[span]]s. Finally, there is a simple observation on the [[cartesian product]] on [[over category|over categories]]: for \begin{displaymath} \itexarray{ && Y \\ && \downarrow^g \\ X &\stackrel{f}{\to}& Z } \end{displaymath} a diagram in $\mathbf{H}$, notice that the objects in the [[fiber product]] of [[over category|over categories]] \begin{displaymath} (\mathbf{H}/X) \times_{\mathbf{H}/Y} \mathbf{H}/Y \end{displaymath} are those pairs $\psi : \Psi \to X$ and $\phi : \Phi \to Y$ such that we get a (homotopy) commutative diagram \begin{displaymath} \itexarray{ \Psi \simeq \Phi &\stackrel{\phi}{\to}& Y \\ \downarrow^\psi && \downarrow^g \\ X &\stackrel{f}{\to}& Z } \,. \end{displaymath} Again by the universal property of the pullback this is the same as maps \begin{displaymath} (\Psi \simeq \Phi) \to X \times_Z Y \end{displaymath} which are precisely the objects of $C(X \times_Z Y)$. So we get \begin{displaymath} C(X \times_Z Y) \simeq C(X) \times_{C(Z)} C(Y) \end{displaymath} \hypertarget{remarks}{}\subsubsection*{{remarks}}\label{remarks} \begin{itemize}% \item This is -- more or less implicitly -- the notion of geometric ∞-functions that underlies [[John Baez]]` notion of [[groupoidification]] as well as the generalized sections that appear at \href{http://ncatlab.org/schreiber/show/Nonabelian+cocycles+and+their+sigma+model+QFTs}{these sigma-model notes}. \item The definition seems to be disturbingly non-linearized, but this should be viewed in light of the possible nature of the $X$s considered here. If $X = E$ is, for instance, the [[groupoid]] incarnation of the total space of the [[vector bundle]] associated to a $G$-[[principal bundle]], then a choice of groupoid over $E$ picks a bunch of vectors in that bundle, hence picks a ``distributional section'' of that bundle. \end{itemize} \hypertarget{undercategories_of_quantities}{}\subsection*{{under-categories of $\infty$-quantities}}\label{undercategories_of_quantities} By essentially simply applying [[Isbell duality]] for the case that the underlying [[site]] is [[CartSp]] to the above example one obtains the following example. Tentative. Recall the notion of [[∞-quantity]]. Notice that by the discussion at [[models for ∞-stack (∞,1)-toposes]] every object $A \in \mathbf{H}$ may be modeled as a [[simplicial presheaf]]. Let $C^\infty(-)$ be the map that sends simplicial presheaves to cosimplicial copresheaves as described at [[∞-quantity]]. Then consider the assignment \begin{displaymath} C(-) : \mathbf{H} \to (\infty,1)Cat \end{displaymath} that sends every $X$ to the $(\infty,1)$-category of cosimplicial copresheaves to the [[under category]] \begin{displaymath} C(X) = C^\infty(X)/CoSCoSh \end{displaymath} or \begin{displaymath} C(X) = C^\infty_{loc}(X)/CoSCoSh \,. \end{displaymath} From the discussion at [[∞-quantity]] and [[Lie-∞ algebroid representation]] we see that we can think of objects in $C(X)$ defines this way as representations of the [[Lie-∞ algebroid]] of $X$. Now pullback is left adjoint and push-forward is right adjoint. \hypertarget{quasicoherent_sheaves}{}\subsection*{{quasicoherent sheaves}}\label{quasicoherent_sheaves} The choice $C(X) =$ the [[stable (∞,1)-category]] of [[quasicoherent sheaf|quasicoherent sheaves]] on a [[derived stack]] $X$ is discussed at \begin{itemize}% \item [[geometric ∞-function theory]]. \end{itemize} [[!redirects examples for geometric function objects]] [[!redirects example for geometric function objects]] [[!redirects geometric function objects]] \end{document}