diff --git a/database/data/categories/Quiv_fc.yaml b/database/data/categories/Quiv_fc.yaml index 16bffbe7a..fbe4ecf44 100644 --- a/database/data/categories/Quiv_fc.yaml +++ b/database/data/categories/Quiv_fc.yaml @@ -42,6 +42,7 @@ satisfied_properties: - property: coequalizers of kernel pairs proof: 'Let $f : G \to H$ be a morphism in $\Quiv_{\fc}$. In $\Quiv$, the coequalizer of the kernel pair of $f$ is simply the image of $f$. Since $\Quiv_{\fc} \subseteq \Quiv$ is closed under subquivers, this image belongs to $\Quiv_{\fc}$. The universal property of a coequalizer persists in $\Quiv_{\fc}$.' + check_redundancy: false - property: extremal cogenerating collection proof: >- @@ -50,11 +51,12 @@ satisfied_properties: Remark: The same proof works for $\Quiv$. label: Quiv_fc_extremal_cogenerators - - property: well-copowered - proof: This follows immediately from the description of epimorphisms below. - - property: epi-regular proof: Any epimorphism $f = (f_V,f_E)$ in $\Quiv_{\fc}$ has surjective components $f_V,f_E$ by the classification below. Hence, it is the coequalizer of its kernel pair in $\Quiv$. Since the kernel pair belongs to $\Quiv_{\fc}$, it is also the coequalizer in $\Quiv_{\fc}$. + check_redundancy: false + + - property: regular + proof: We already know that $\Quiv_{\fc}$ is finitely complete, has coequalizers of kernel pairs, and that every epimorphism is regular. So it remains to show that epimorphisms are stable under pullbacks. Pullbacks in $\Quiv_{\fc}$ are computed as in $\Quiv$ (see the proofs above), i.e. separately on vertices and edges. By the classification below, the epimorphisms are the morphisms $f = (f_V,f_E)$ with surjective components $f_V,f_E$. Since surjective maps are stable under pullbacks in $\Set$, the claim follows. - property: ℵ₁-accessible proof: >- diff --git a/database/data/category-implications/congruences.yaml b/database/data/category-implications/congruences.yaml index 965e3311b..5e6db445c 100644 --- a/database/data/category-implications/congruences.yaml +++ b/database/data/category-implications/congruences.yaml @@ -110,10 +110,12 @@ - epi-regular - extensive - regular + - finitely cocomplete conclusions: - co-Malcev - effective cocongruences proof: >- + We need to show that every coreflexive corelation is an effective cocongruence. Suppose we have a coreflexive corelation $$X+X' \xtwoheadrightarrow{p} E \xtwoheadrightarrow{r} X$$ on $X$, where we let $X'$ be an isomorphic copy of $X$ for clarity below. Let $Y$ be the equalizer of $p\circ i_1, p\circ i_2 : X \rightrightarrows E$. That means that for a generalized element $x \in X(T)$, $x \in Y(T)$ if and only if $p(x) = p(x')$. Then by the assumptions $p$ is a regular epimorphism. By this lemma, $p$ is the coequalizer of its kernel pair, which can be expressed as the equalizer $K$ of