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\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*{coherent (infinity,1)-topos} \hypertarget{context}{}\subsubsection*{{Context}}\label{context} \hypertarget{topos_theory}{}\paragraph*{{$(\infty,1)$-Topos Theory}}\label{topos_theory} [[!include (infinity,1)-topos - contents]] \hypertarget{compact_objects}{}\paragraph*{{Compact objects}}\label{compact_objects} [[!include compact object - contents]] \hypertarget{contents}{}\section*{{Contents}}\label{contents} \noindent\hyperlink{idea}{Idea}\dotfill \pageref*{idea} \linebreak \noindent\hyperlink{definitions}{Definitions}\dotfill \pageref*{definitions} \linebreak \noindent\hyperlink{properties}{Properties}\dotfill \pageref*{properties} \linebreak \noindent\hyperlink{commutativity_with_filtered_colimits}{Commutativity with filtered colimits}\dotfill \pageref*{commutativity_with_filtered_colimits} \linebreak \noindent\hyperlink{in_terms_of_sites}{In terms of sites}\dotfill \pageref*{in_terms_of_sites} \linebreak \noindent\hyperlink{delignelurie_completeness_theorem}{Deligne-Lurie completeness theorem}\dotfill \pageref*{delignelurie_completeness_theorem} \linebreak \noindent\hyperlink{Examples}{Examples}\dotfill \pageref*{Examples} \linebreak \noindent\hyperlink{references}{References}\dotfill \pageref*{references} \linebreak \hypertarget{idea}{}\subsection*{{Idea}}\label{idea} The concept of \emph{coherent $(\infty,1)$-topos} is a notion of \emph{[[compact topos]]} in the context of [[(∞,1)-topos theory]] ([[Spectral Schemes|Lurie VII, def. 3.1]]). \hypertarget{definitions}{}\subsection*{{Definitions}}\label{definitions} \begin{defn} \label{}\hypertarget{}{} An (∞,1)-topos $\mathbf{H}$ is called \textbf{[[quasicompact morphism|quasi-compact]]} if, for every [[effective epimorphism]] \begin{displaymath} \coprod_{i\in I} U_i\to * \end{displaymath} there exists a [[finite set|finite]] [[subset]] $J\subset I$ such that $\coprod_{i\in J} U_i\to *$ is an effective epimorphism. An object $X\in\mathbf{H}$ is called quasi-compact if the [[slice (∞,1)-topos]] $\mathbf{H}_{/X}$ is quasi-compact. \end{defn} We then define $n$-coherence by [[induction]] on $n$. \begin{defn} \label{nCoherentTopos}\hypertarget{nCoherentTopos}{} Let $\mathbf{H}$ be an [[(∞,1)-topos]]. We say that $\mathbf{H}$ is 0-coherent if it is quasi-compact. If $n\geq 1$, we say that $\mathbf{H}$ is \textbf{n-coherent} if \begin{enumerate}% \item it is \textbf{locally $(n-1)$-coherent}, i.e., for every $X\in\mathbf{H}$ there exists an effective epimorphism $\coprod_{i\in I} U_i\to X$ such that each $U_i$ is (n-1)-coherent; \item the [[sub-(∞,1)-category]] of (n-1)-coherent objects in $\mathbf{H}$ is closed under [[finite products]]. \end{enumerate} We say that $\mathbf{H}$ is \textbf{coherent} if it is $n$-coherent for every $n\geq 0$, and \textbf{locally coherent} if for every $X\in\mathbf{H}$ there exists an effective epimorphism $\coprod_{i\in I} U_i\to X$ such that each $U_i$ is coherent. \end{defn} ([[Spectral Schemes|Lurie SpecSch, def. 3.1, def. 3.12]]) \begin{remark} \label{}\hypertarget{}{} This terminology differs from the one in [[SGA]]4: a [[topos]] is a [[coherent topos]] in the sense of [[SGA]]4 if and only if it is 2-coherent according to the above definition. \end{remark} \begin{defn} \label{}\hypertarget{}{} An [[object]] $X \in \mathcal{X}$ in an [[(∞,1)-topos]] is a \emph{[[n-coherent object]]} if the [[slice (∞,1)-topos]] $\mathcal{X}_{/X}$ is $n$-coherent according to def. \ref{nCoherentTopos}. \end{defn} \hypertarget{properties}{}\subsection*{{Properties}}\label{properties} \hypertarget{commutativity_with_filtered_colimits}{}\subsubsection*{{Commutativity with filtered colimits}}\label{commutativity_with_filtered_colimits} Notice that a [[compact object in an (∞,1)-category]] is one that distributes over [[filtered (∞,1)-colimits]]. In an $n$-coherent $\infty$-topos the [[global section geometric morphism]] (given by homming out of the [[terminal object]]) preserves [[filtered (∞,1)-colimits]] of [[truncated object in an (infinity,1)-topos|(n-1)-truncated objects]]. \hypertarget{in_terms_of_sites}{}\subsubsection*{{In terms of sites}}\label{in_terms_of_sites} An [[(∞,1)-site]] is \emph{finitary} if every [[covering]] [[sieve]] is generated by a finite family of morphisms. If $C$ is a finitary (∞,1)-site with [[finite (∞,1)-limits]], then the [[(∞,1)-topos of (∞,1)-sheaves]] on $C$ is coherent and locally coherent. \hypertarget{delignelurie_completeness_theorem}{}\subsubsection*{{Deligne-Lurie completeness theorem}}\label{delignelurie_completeness_theorem} The following generalizes the [[Deligne completeness theorem]] from [[topos theory]] to [[(∞,1)-topos theory]]. \begin{theorem} \label{}\hypertarget{}{} \textbf{[[Deligne-Lurie completeness theorem]]} An [[hypercomplete (∞,1)-topos]] which is locally coherent has [[enough points]]. \end{theorem} ([[Spectral Schemes|Lurie SpecSchm, theorem 4.1]]). \hypertarget{Examples}{}\subsection*{{Examples}}\label{Examples} \begin{example} \label{}\hypertarget{}{} [[∞Grpd]] is coherent and locally coherent. An [[object]] $X$, hence an [[∞-groupoid]], is an [[n-coherent object]] if all its [[homotopy groups]] in degree $k \leq n$ are [[finite set|finite]]. Hence the fully coherent objects here are the [[homotopy types with finite homotopy groups]]. \end{example} ([[Spectral Schemes|Lurie SpecSchm, example 3.13]]) \begin{example} \label{}\hypertarget{}{} Let $X$ be a [[scheme]] and let $Sh_\infty(X_{Zar})$ be the [[(∞,1)-topos of (∞,1)-sheaves]] on the [[small site|small]] [[Zariski site]] of $X$. Then the following assertions are equivalent: \begin{enumerate}% \item $Sh_\infty(X_{Zar})$ is coherent; \item $Sh_\infty(X_{Zar})$ is 1-coherent; \item $X$ is quasi-compact and quasi-separated. \end{enumerate} \end{example} \begin{example} \label{}\hypertarget{}{} A [[spectral scheme]] or [[spectral Deligne-Mumford stack]], regarded as a [[structured (∞,1)-topos]] is locally coherent. \end{example} ([[Quasi-Coherent Sheaves and Tannaka Duality Theorems|Lurie QCoh, cor. 1.4.3]]) \hypertarget{references}{}\subsection*{{References}}\label{references} \begin{itemize}% \item [[Jacob Lurie]], section 3 of \emph{[[Spectral Schemes]]} \item [[Jacob Lurie]], section 2.3 of \emph{[[Rational and p-adic Homotopy Theory]]} \item [[Jacob Lurie]], \emph{[[Quasi-Coherent Sheaves and Tannaka Duality Theorems]]} \end{itemize} [[!redirects coherent (infinity,1)-toposes]] [[!redirects coherent (∞,1)-topos]] [[!redirects coherent (∞,1)-toposes]] [[!redirects n-coherent (∞,1)-topos]] [[!redirects n-coherent (infinity,1)-topos]] [[!redirects n-coherent (∞,1)-toposes]] [[!redirects n-coherent (infinity,1)-toposes]] [[!redirects locally coherent (∞,1)-topos]] [[!redirects locally coherent (∞,1)-toposes]] [[!redirects locally n-coherent (∞,1)-topos]] [[!redirects locally n-coherent (infinity,1)-topos]] [[!redirects locally n-coherent (∞,1)-toposes]] [[!redirects locally n-coherent (infinity,1)-toposes]] \end{document}