<p>A basic technique in model theory is to name the elements of a model by introducing new constant symbols. We describe the analogous construction in the language of syntactic categories/sites. As an application we identify <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textbf{Set}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">Set</mi> </math></EquationSource> </InlineEquation>-valued regular functors on the syntactic category with a certain class of topos-valued models (we will refer to them as "<i>Sh</i>(<i>B</i>)-valued models"). For the coherent fragment <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq5.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="80" /> </InlineMediaObject> <EquationSource Format="TEX">\(L_{\omega \omega }^g \subseteq L_{\omega \omega }\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>L</mi> <mrow> <mi>ω</mi> <mi>ω</mi> </mrow> <mi>g</mi> </msubsup> <mo>⊆</mo> <msub> <mi>L</mi> <mrow> <mi>ω</mi> <mi>ω</mi> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> this was proved by Jacob Lurie, our discussion gives a new proof, together with a generalization to <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq6.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(L_{\kappa \kappa }^g\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>L</mi> <mrow> <mi>κ</mi> <mi>κ</mi> </mrow> <mi>g</mi> </msubsup> </math></EquationSource> </InlineEquation> when <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq7.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\kappa \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>κ</mi> </math></EquationSource> </InlineEquation> is weakly compact. We present some further applications: first, a <i>Sh</i>(<i>B</i>)-valued completeness theorem for <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq8.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(L_{\kappa \kappa }^g\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>L</mi> <mrow> <mi>κ</mi> <mi>κ</mi> </mrow> <mi>g</mi> </msubsup> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq9.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\kappa \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>κ</mi> </math></EquationSource> </InlineEquation> is weakly compact), second, that <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10485_2025_9804_Article_IEq10.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="65" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {C}\rightarrow \textbf{Set} \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">C</mi> <mo stretchy="false">→</mo> <mi mathvariant="bold">Set</mi> </mrow> </math></EquationSource> </InlineEquation> regular functors (on coherent categories with disjoint coproducts) admit an elementary map to a product of coherent functors.</p>

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Sh(B)-Valued Models of \((\kappa ,\kappa )\)-Coherent Categories

  • Kristóf Kanalas

摘要

A basic technique in model theory is to name the elements of a model by introducing new constant symbols. We describe the analogous construction in the language of syntactic categories/sites. As an application we identify \(\textbf{Set}\) Set -valued regular functors on the syntactic category with a certain class of topos-valued models (we will refer to them as "Sh(B)-valued models"). For the coherent fragment \(L_{\omega \omega }^g \subseteq L_{\omega \omega }\) L ω ω g L ω ω this was proved by Jacob Lurie, our discussion gives a new proof, together with a generalization to \(L_{\kappa \kappa }^g\) L κ κ g when \(\kappa \) κ is weakly compact. We present some further applications: first, a Sh(B)-valued completeness theorem for \(L_{\kappa \kappa }^g\) L κ κ g ( \(\kappa \) κ is weakly compact), second, that \(\mathcal {C}\rightarrow \textbf{Set} \) C Set regular functors (on coherent categories with disjoint coproducts) admit an elementary map to a product of coherent functors.